I'll echo Stamet's statements (heh). The vitriol for the sequels, if anything, is softer in a lot of ways than it was for the sequels.

Jake Lloyd was massively bullied (by classmates and fans) to the point he wanted nothing to do with any of it. Ahmed Best has been pretty open about considering suicide. Hayden Christensen got a lot of hate as well. It's hard to find raw things from the era unless you happen to know forum links and such. The article below makes it seem a lot smoother but I think the quoted bit helps a little.

And then again, at the end:

[In his home], he has a series of large metal letters that spell out a motto: ILLEGITIMI NON CARBORUNDUM. “It was a saying among soldiers in World War II,” he explains. “It means ‘Don’t let the bastards get you down.’”

As far as RotJ it's hard to understand how much the die hard fans hated the Ewoks now. Imagine the criticisms you raised above being focused onto a single portion of one movie. The anger I've seen over Canto Bight being unnecessary doesn't even touch it.

It's absolutely an age thing and I'm confident the sequels in twenty years will be largely as received as the prequels are now and you can have this side of the conversation with some young fan upset with the new thing that's ruining all of it.