I dont think the Jedi are a dictatorial power in Lucas' eyes. They're the knights of the round table more than they are the samurai (though they are very eastern in many other respects- samurai were military dictators and the Jedi are not).
I think the Jedi had become too calcified, too bound by tradition rather than something natural.
In Episode I we see Yoda living in a palace, surrounded by opulence, being carted around on hoverpads. The down to earth Jedi, Qui Gon, is not a leader of the Jedi because he speaks his mind too much.
Obi Wan's frustrated "but you'd be on the council already if only..." lets us know that politics has come to play a larger role in who leads the Jedi that knowledge of the force and wisdom. There's a worm in the apple and that worm is one of the reasons why they don't see the dangers right in front of their eyes, both Anakin and Palpatine.
Compare that to the rustic life he and Obi Wan are living in Episode IV- they are much simpler, much more down to earth. They are living like monks not kings.
Remember that to the Jedi, Anakin bringing "balance" to the force was seen as a GOOD prophecy. They clearly speak of it that way throughout the films.
They don't realize that it IS a good thing but the balancing entails losing all the trappings of opulence. No thousands of super-men at the Jedi Council's beck and call.
The field has been burned so a new crop, planted by Luke can be planted.