Over sexualization of minors is one of those things that can make it hard(and embarrassing) to be an anime/manga fan.
For high school characters at least(depending on the series) you can usually rationalize it the same way you might with an american show that hires adult actors. Theyre intentionally drawn in a more adult fashion and the characters themselves, while exhibiting cute traits are often still hyper competent and independent in a way that resembles college students more than high schoolers.
Is it still conceptually gross? Absolutely. It's something that you just get desensitized to and I dont think thats a good thing, but at least on some level I can see how it can be tolerated in SOME series depending on how it's handled, but I can also see how it's a deal breaker.
The full on child stuff full stop is gross. All the time. There is no desensitizing and I hate that its so goddamn common in anime and that it's so accepted. To the point that the community has a cute little term for sexualized children that they throw around. In any other community this would be a fringe dark corner of the hobby that never touches the more mainstream stuff, but in anime land it's front and center.