Well, I suppose the first thing to point out is that your opinion of whether TLJ was “this bad” is pretty subjective. I personally think it is one of the better Star Wars movies and poops over any of the prequel movies. And that is the point of the HT, rather than making fun of the movie itself, it makes fun of just how polarising the movie was. Just look at the fact that they used two narrators representing polar opposites of opinions. They point out both the bad and the good in the movie. Is the movie full of plot holes? Of course, just like any other Star Wars movie. Does it waste out time with boring sub plots? Well, yes, so does every prequel movie. Does it follow the basic formula of eps 4, 5 and 6? Yes. But again, so do the prequels.
I know I bang on about this but it just amazes me how so many people shit all over Rian Johnson and TLJ acting like he ruined SW. But people forget, It was already ruined by George Lucas with Pod Racing, Jar Jar Binks, Hayden Christiansen, The entirety of Attack of the Clones, The Jedi Council, How Padme died. I could go on. The beauty of TLJ is that Rian actively addresses the stupidity of the Jedi Council. He echos the things I’ve been shaking my head at for years and tries to correct them like how only Skywalkers can be powerful Jedi. He tried something new within the constraints he had and it worked. It just wasn’t what the fandom had built it up to be.
But I understand how others don’t necessarily like the direction. The plot devices left unexplored from TFA was a little disappointing but I think what was gained in unshackling the characters and story from predetermined outcomes was well worth it.