Well that's a matter of opinion. Though I agree, the Joker was very good.
And there have been a number of movies with excellent production quality that completely bombed, because overall the story wasn't good. It's not all about having the best of everything production wise.
And I'm not saying "yes, let's make everything bad!" I don't know where that came from. I'm saying there's a lot of talk about "high quality" and perfection, which just reminds me of Stepford rather than Muppets. Would you call Hippies clean and pristine and without blemishes imperfections? No, because they're not supposed to be. And neither are the Muppets.
Well 1960s/70s audiences weren't doing peer reviews. They were enjoying what was an excellent product, without having to rely on modern "high quality" that we're all so convinced we need nowadays to tell a story.