EDIT/TLDR - If you really want to narrow the argument down and not "brush" Isekai, perhaps the real issue isn't the genre, it's the recommendations? I'm skeptical but it's possible. What I've seen consistently since my brother got me back into watching anime a couple of years ago, is that where Isekai is recommended, it's often completely terrible, and a non-Isekai show with the same flaws wouldn't get the same kind of recommendation.
I think it is a problem with the recommendations, but more specifically you need to understand who is recommending things and why.
Another subgenre that I really, really like is LitRPG, which contains things like cultivation stories and progression fantasy. A major problem with a lot of these stories is the Overpowered Protagonist. It is REALLY prevalent, and it annoys me in a lot of cases. There was a story I read not too long ago that I thought was going to be an interesting story about a merchant, and ended up with him slaying a high-ranking angel and then that angel's god by the end of the first book. It was just too much for me.
But the story Azarinth Healer ALSO has a very overpowered protagonist in a lot of ways, who by the end of the third book has left everything she was doing in the first book far behind, and has even successfully regenerated from being beheaded. It is a trope I normally hate... but it was done well and it didn't annoy me in THAT book. Nor would I think people who hate overpowered protagonists would necessarily hate One-Punch Man, who is explicitly ludicrously overpowered. So, if I was recommending those stories, I could be rightfully accused of recommending stories with a bad and even harmful trope... but I wouldn't be recommending them FOR that trope.
Do people who recommend these bad Isekai do so because they LIKE overpowered male fantasies? Maybe. I know a lot of people recommend Konosuba, but they aren't recommending it because it has well-written plots with likable characters... they recommend it because they find it funny. If you don't like the humor of the show... you won't like the show. I like Realist Hero, an Isekai that has a harem as a core part of the plot and deals with slavery... but I like how they handled the harem, I don't see anything inherently wrong with polyamorous relationships, and the slavery issue was brief and handled fairly realistically fitting with some of the realpolitik themes of the story. I tried watching Overlord, but I found it boring and I lost interest. I know many people love it. I don't begrudge them that, but it wasn't for me.
Again, if you were simply saying "Many of the most popular Isekai I don't think are any good, and are full of nasty tropes"... I can't disagree with that. Rise of a Shield Hero is something I missed, but the more I hear about it, the more I am glad that I missed it. Maybe it would have charmed me if I saw it, maybe it would have really bothered me, I don't know. And I don't think you are talking out of ignorance, because I recognize you are correct about a large number of your points. I just think you go too far. Just like I think people go too far with Urban Fantasy, just like I think people go too far with LitRPG stories. Yes, there is a lot of garbage out there. But that garbage is not an innate feature baked into the genre and inseperable from it. The good stories are not "exceptions that prove the rule" they are... good stories in that genre. I mean heck, there are good and bad adaptations of sherlock holmes, there are good and bad comedy sitcoms, there are good and bad reality tv shows (I'm sure there is at least one good one). The message of "be careful with the genre, because it has a lot of crappy shows in it" is fair. The message of "this genre is crap and it should burn to the gorund, because it is inherently bad"... isn't. I'd lose too many shows that are exquisitely made or at least really interesting if you did that.