His entire class of pupils are murdered and he doesn’t really seem that shocked. He just heads over to Palpy for a few extra force power moves before quitting. He might has well have said “failed to do enough flips to beat him I have”.
100%. “Failed I have”, in the context of the movie, is not some grander statement on his role in the Jedi, he’s literally just talking about how he lost the dance-off with Ian McDiarmid.
This interpretation of Yoda’s character arc, it’s cool and all, but it’s not at all present in the prequels.