Endless problems, but one of the worst is the portrayal of Jedi. I agree with others that they should be more detached and remote, like samurai. A meeting with Yoda should be a special and mysterious trip, like meeting with Nicodemus of the rats of NIMH. But most of all, the Jedi Temple was a horrendous mistake.
The Jedi are a religion of life. Yoda has his whole famous speech about how the Force grows from the life in the universe. Why else would he live in Dagobah? That planet is absolutely dripping with living things. So where does George place the Jedi to worship? In a steel and marble monstrosity that doesn't have so much as a potted plant. AND the council meets in a chamber at the tippy-top of the highest tower, as far as possible from the life-sustaining earth below. A true Jedi would HATE IT in that place. It's a chilly, lifeless hell.
That's really not the worst mistake in the PT, but it exemplifies the thoughtlessness that infects everything else. Literally - he just did things without thinking about what they meant.