^ funnyjunk link fail.
There are flaws unique to ROTJ some of them are down to attempting things technically that just don't work.
The little motorised puppet pilots in the snowspeeders would look just as crap as the stop motion puppets on the sail barge if they weren't covered by the cockpit hatch.
And the barge explosion (even after being tinkered with for the various SEs still looks awful).
The AOTC speeder is a real prop on fire on a set so it looks more real than stop motion puppets on a model matted onto an exploding model shot (especially with the original matte lines).
But a lot of it is down to Lucas just losing his mojo.
Just compare the amount of attention ILM put into making Raiders the amazing natural feeling piece of escapism it was and compare it TOD and TLC.
He went into Star Wars hoping to rebel against the studio system and have fun.
His marriage broke down and he ended up ruling an Empire of his own.
It's no surprise that after the lackluster 'finish everything quick' ROTJ the only kind of Star Wars Lucas had left in him was a boring tale about a kid who screws up his marriage and ends up being the evil he swore to fight against.
Willow is a better Star Wars film than Jedi and that too is not without major flaws.