At whose hand should change be wrought at a time when the situation of the Muslims contradicts the greatness of their religion?

There is no doubt concerning the universal truth that you have mentioned. Justice between people is a general principle of sharee’ah which applies to everyone, both believer and non-believer, those whom we love and those whom we hate. Allaah says (interpretation of the meaning): 

“O you who believe! Stand out firmly for Allaah as just witnesses; and let not the enmity and hatred of others make you avoid justice. Be just: that is nearer to piety; and fear Allaah. Verily, Allaah is Well‑Acquainted with what you do”

[al-Maa’idah 5:8] 

“So unto this (religion of Islam alone and this Qur’aan) then invite (people) (O Muhammad), and stand firm (on Islamic Monotheism) as you are commanded, and follow not their desires but say: “I believe in whatsoever Allaah has sent down of the Book [all the holy Books, this Qur’aan and the Books of the old from the Tawraat (Torah), or the Injeel (Gospel) or the Pages of Ibraaheem (Abraham)] and I am commanded to do justice among you. Allaah is our Lord and your Lord. For us our deeds and for you your deeds. There is no dispute between us and you. Allaah will assemble us (all), and to Him is the final return”

[al-Shoora 42:15] 

There is also no doubt that mankind has no hope of being saved from its problems or of being guided and saved from misguidance except through this religion. Allaah says (interpretation of the meaning): 

“Such is Allaah, your Lord in truth. So after the truth, what else can there be, save error? How then are you turned away?”

[Yoonus 10:32]

 “And if the people of the towns had believed and had the Taqwa (piety), certainly, We should have opened for them blessings from the heaven and the earth, but they belied (the Messengers). So We took them (with punishment) for what they used to earn (polytheism and crimes)”

[al-A’raaf 7:96]

It is not only that mankind will not prosper if they follow this religion and will be corrupted if they forsake it, because of its justice which encompasses all creatures, rather the most fundamental principles that will enable mankind to prosper is the principle of pure Tawheed, the belief that the Lord of the Worlds is One, on which this religion is based. So there is no submission to any angel or jinn, or to any human being or rock. Just as there cannot be more than one creator for this universe, so too there cannot be more than one controller, who is Allaah, may He be glorified. Allaah says (interpretation of the meaning): 

“Indeed, your Lord is Allaah, Who created the heavens and the earth in Six Days, and then He rose over (Istawa) the Throne (really in a manner that suits His Majesty). He brings the night as a cover over the day, seeking it rapidly, and (He created) the sun, the moon, the stars subjected to His Command. Surely, His is the creation and commandment. Blessed is Allaah, the Lord of the ‘Aalameen (mankind, jinn and all that exists)!”

[al-A’raaf 7:54]

“Had there been therein (in the heavens and the earth) aalihah (gods) besides Allaah, then verily, both would have been ruined. Glorified be Allaah, the Lord of the Throne, (High is He) above all that (evil) they associate with Him!”

[al-Anbiya’ 21:22]

Mankind’s deviation from this great principle is the greatest cause of the confusion and misguidance in which they are living and the misery that has overtaken them. Allaah says (interpretation of the meaning): 

“Say (O Muhammad): ‘Shall we invoke others besides Allaah (false deities), that can do us neither good nor harm, and shall we turn back on our heels after Allaah has guided us (to true Monotheism)? — like one whom the Shayaateen (devils) have made to go astray in the land in confusion, his companions calling him to guidance (saying): Come to us.’  Say: ‘Verily, Allaah’s Guidance is the only guidance, and we have been commanded to submit (ourselves) to the Lord of the ‘Aalameen (mankind, jinn and all that exists)’”

[al-An’aam 6:71]

“But whosoever turns away from My Reminder (i.e. neither believes in this Qur’aan nor acts on its teachings) verily, for him is a life of hardship, and We shall raise him up blind on the Day of Resurrection.”

125. He will say: ‘O my Lord! Why have you raised me up blind, while I had sight (before).’

126. (Allaah) will say: ‘Like this: Our Ayaat (proofs, evidences, verses, lessons, signs, revelations, etc.) came unto you, but you disregarded them (i.e. you left them, did not think deeply in them, and you turned away from them), and so this Day, you will be neglected (in the Hell‑fire, away from Allaah’s Mercy).’

127. And thus do We requite him who transgresses beyond bounds [i.e. commits the great sins and disobeys his Lord (Allaah) and believes not in His Messengers, and His revealed Books, like this Qur’aan], and believes not in the Ayaat (proofs, evidences, verses, lessons, signs, revelations, etc.) of his Lord; and the torment of the Hereafter is far more severe and more lasting”

[Ta-Ha 20:124-127]

By Allaah’s wisdom, there are two types of people: believers and disbelievers, obedient and disobedient, and by His wisdom the one is checked by means of the other. Allaah says (interpretation of the meaning): 

“And if Allaah did not check one set of people by means of another, the earth would indeed be full of mischief. But Allaah is full of bounty to the ‘Aalameen (mankind, jinn and all that exists)”

[al-Baqarah 2:251]

“For had it not been that Allaah checks one set of people by means of another, monasteries, churches, synagogues, and mosques, wherein the Name of Allaah is mentioned much would surely, have been pulled down. Verily, Allaah will help those who help His (Cause). Truly, Allaah is All‑Strong, All‑Mighty”

[al-Hajj 22:40]

Allaah is most wise in that, for He distinguishes the sincere from the liar, so that Allaah may know who will support Him (His cause) and His Messengers, and who will oppose Him and wage war against Him. This is the reason behind trials in this life: 

“but if it had been Allaah’s Will, He Himself could certainly have punished them (without you). But (He lets you fight) in order to test some of you with others. But those who are killed in the way of Allaah, He will never let their deeds be lost”

[Muhammad 47:4]

What you have referred to, the fact that many Muslims have gone astray from the teachings of their religion, is true of most Muslims today, except for those on whom their Lord has mercy, the saved group who adhere to the truth. This is the greatest trial that we are faced with at this time, and it is the cause of the weakness and humiliation that the Muslims are suffering from, and their being dominated by their enemies. The Prophet (peace and blessings of Allaah be upon him) said: “When you enter into the ‘aynah transaction, hold onto the tails of oxen, are content with agriculture, and give up jihad, Allaahwill cause disgrace to prevail over you, and will notwithdraw it until you return to your (true) religion.” Narrated by Abu Dawood, 3462; classed as saheeh by al-Albaani in al-Saheehah, 11. 

Allaah has warned His slaves in more than one verse of His Book, of the punishment for being negligent with regard to their religion and of being careless with regard to the trust that He has placed on their shoulders. He has warned them that the consequences of that will come back on them, and the loss will be theirs. As for the religion of Allaah, it is protected by Allaah. Allaah says (interpretation of the meaning): 

“Muhammad is no more than a Messenger, and indeed (many) Messengers have passed away before him. If he dies or is killed, will you then turn back on your heels (as disbelievers)? And he who turns back on his heels, not the least harm will he do to Allaah; and Allaah will give reward to those who are grateful”

[Aal ‘Imraan 3:144]

When the lazy generation moves on, those who away from the battlefield and neglected their trust, then will come the turn of those who are chosen for this mission, whom Allaah has honoured by entrusting them with His religion: 

“O you who believe! Whoever from among you turns back from his religion (Islam), Allaah will bring a people whom He will love and they will love Him; humble towards the believers, stern towards the disbelievers, fighting in the way of Allaah, and never fear of the blame of the blamers. That is the Grace of Allaah which He bestows on whom He wills. And Allaah is All‑Sufficient for His creatures’ needs, All‑Knower”

[al-Maa’idah 5:54]

“Behold! You are those who are called to spend in the Cause of Allaah, yet among you are some who are niggardly. And whoever is niggardly, it is only at the expense of his ownself. But Allaah is Rich (Free of all needs), and you (mankind) are poor. And if you turn away (from Islam and the obedience to Allaah), He will exchange you for some other people and they will not be your likes”

[Muhammad 47:38]

But we reiterate that this new generation will be from among the Muslims themselves, not from any other nation. There will not be angels who come down to take up the mission that people have neglected.  

There will not be a miracle that makes lazy people victorious.  And there will never be a generation among the kuffaar who support the religion of Allaah. Allaah and His religion have no supporters and helpers except the pious. When that generation comes, then will come the help of Allaah: 

“O you who believe! If you help (in the cause of) Allaah, He will help you, and make your foothold firm”

[Muhammad 47:7]

It is up to us to renew ourselves, to train our children and families, to call others, so that we will be part of this generation or at least a step in the right direction. 

We ask Allaah to help us to do that which He loves and which pleases Him and to support His religion through us. And Allaah knows best.