But I must also thank Benedict for one thing, namely making an effort to revive the music of the church
I think all the recent pontiffs have contributed greatly to the development of doctrine and to the richness of the sacred tradition, just differently.
Benedict XVI's 2009 encyclical
Caritas was for instance an excoriating indictment of the pitfalls of the global financial order and liberal capitalism, that Francis has very much built upon and expounded in his own way.
For example, many critics of Francis in America allege that he is a "Marxist" sympathiser but it was actually Benedict who wrote a positive appraisal of democratic socialism in 2006:
Democratic socialism managed to fit within the two existing models as a welcome counterweight to the radical liberal positions, which it developed and corrected. It also managed to appeal to various denominations. In England it became the political party of the Catholics, who had never felt at home among either the Protestant conservatives or the liberals. In Wilhelmine Germany, too, Catholic groups felt closer to democratic socialism than to the rigidly Prussian and Protestant conservative forces. In many respects, democratic socialism was and is close to Catholic social doctrine and has in any case made a remarkable contribution to the formation of a social consciousness.
Those words were
penned by Pope Benedict XVI in an essay published at First Things back in 2006.
John Paul II, likewise, was notably exemplary in putting interreligious dialogue at the forefront of church relations with the rest of the world. He really took
Nostra Aetate's teaching that "seeds of the truth" were to be found in all religions and all people to heart more than any of his predecessors, and endured a lot of hate from traditionalists for doing things like blessing Quran's, statutes of the Buddha and other such things that many on the right found offensive.
But Francis has still taken a very bold step away from his predecessors fixation with sexual morality, dogmatic judgment
and their hierocratic understanding of their office. He has taken some inspiration from liberation theology in South America, quite clearly, even inviting it's founder for a private papal audience and exalting elements of it that had been relegated for perceived conflicts with orthodoxy, by emphasising a truly Christian (rather than Marxist) iteration of it.
And all the other things already mentioned in this thread.