Out of all the tropes in anime, THIS is the one that you have the biggest issue with? What about the borderline pedophile tropes or cringe fanservice? That being said, I do watch anime, but just saying that the fanservice is my biggest issue with them, by far.
Borderline? A lot of these are straight up apologetic. "Oh, it's okay for protagonist-kun to have sex with 13 year-old-chan because he's in the body of a 13 year old himself, which means he has the mentality of a 13 year old." Okay, cool...how many years of life has he personally experienced? 42, you say? Interesting....why don't you have a seat over here, random light-novel author-san?
There are ways to make this slightly less black and white, but most of the time the author doesn't do it because giving the main character mental health issues / memory loss takes a considerable amount of effort and can easily come off as making fun of the irl equivalents.
If the main character only had the memories of their previous life, none of the personality, extremely little of the wisdom, none of the muscle memory/ automatic responses, and pretty much needed flashbacks to remember anything from their previous life (eg. remembering witnessing someone's death being a way of remembering that walking alone at night is dangerous, potentially also having modern police or weapons be shown leading to the main character questioning where these memories were from) or at least extreme emotion attached to the memory (eg. The main character encountering fireworks, making them feel happy/ nostalgic while their peers are terrified of the loud noises). Essentially what I guess I'm trying to say is in my opinion if the previous life was treated like an illness instead of just who they are cross age relationships in isekai would have more complexity to their morality.
Yup, I have the same problems with anime. I just can't stand the cringe fanservice, people actually like that? I have dropped so many anime because of the constant fanservive or the borderline pedophile. It's sad that even anime that's considered "serious" or "high quality".
Just the other day, decided to what this new anime about a demon lord vs hero kind of thing. Episode 1, the Demon lord's side kick is a teenage girl wearing a elementary school swimsuit with sleeves and collar. And then in a conversation scene, the camera angle is......you guess it......from behind the girl and looking up at the girl's ass for no fucking reason. Dropped instantly.