It's not the genre, it's the writing. Just because sausages are usually sold at a hotdog stand doesn't mean it's only a street-food level ingredient; there is always a place for some Michelin star gourmet bangers and mash or whatever.

There is an obvious retort about Narnia being an isekai, but I feel a more appropriate comparison would be Ascendence of a Bookworm, which is an actually well written Japanese isekai literature (written by a female author and featuring a female protagonist, ironic given the main topic) that explores the clash of Earth based norms and customs in a society where gods actually exist, and nobles are literally superior beings, since only their god gifted mana can turn a blank land into fertile soil. In such a world, what value does a mana-less peasant have?

But it does so in a narrative that's engaging rather than scolding; the MC realises that norms arise out of local conditions, and instead of going on some weird emancipation spree, mostly acknowledges local the situations, but still tries her darndest to change things given her constraints (with literal gods intervening, there is little she can do).

The story is titled Ascendence of a 'Bookworm' because her main tool of rebellion is democratising books and knowledge; by inventing the paper and printing press, she will (slowly) help peasants improve their lives over the next coming generations; they will never become equal to nobles who are literally god-gifted, but it's still an important ripple that will change the trajectory of the world.

It's an Japanese isekai, but it resists the urge to dabble in the other other tropes. Yes, Sturgeon's law still applies, 90% of isekai will still be trash and slop, but if you promote good isekai books, then there is still chance for future good literature, even in such a maligned genre.

it's isekai or tiktok, no in-betweens, take it or leave it

The same is true for teen books for girls, where like half of the bestsellers are romantasy, with many of them going into the softcore territory.

I am no pearl clutching moralist, but having the mainstream publishing industry push softcore smut onto young girls and even virtue-signaling about how girls read a lot of books, is not something I'm comfortable with.

It's like selling cigarettes to kids, and bragging about how they seem to like them.

Dungeon Crawler Carl is not the height of literature, but I wouldn't say it's harmful.

That said, I don't have a daughter of reading age, so actual parents might have better takes on this.