I think the whole "the Jedi screwed up" argument feels like a retroactive excuse for sloppy writing on Lucas' part. Sure, you can look at the disconnect between Jedi in the OT and the PT and say, "Well, they learned their lesson," but not much in Empire feels like this is a new method for Yoda.
I actually think this IS an example of sloppy writing, but in this case the sloppiness comes from a failure to have any character state something like "The Jedi aren't what they were, they are kind of fucked up"
But wait, Yoda says just that in AOTC when Obi Wan tells him and Mace Windu that Anakin is arrogant. "Yes, a failing all too common among Jedi, even the older, more experienced ones"
I don't believe I'm defending the Prequels.