I kind of see the "Loser in real world become a winner once isekai-ed" formula with disdain. Especially when they're just happen to be granted a special power and being instantly more expert than everyone else because "I was a gamer" or coming from modern society; without any meaningful character development or struggle whatsoever. The character stays with their 'loser' mindset and personality, while unlike in real world they got no setback from it. It's just trash and uninteresting in my opinionâthe reason we are invested in a story is we want to see character growth, not how they obtain a new plot armor.
Writing technicalities aside, it kind of perpetuate the idea that someone does not need to grow or actively pursue something just wait for a chance to be granted something great and everything will be solved. No need to overcome or get help with depression or anxiety or trauma, you'll be good in RPG world and those mental problems will be cured. I might be reaching, but I feel a bit iffy when those kind of isekai involves death and reincarnation. Things will get better when I die? Oh thank god this rat poison is on sale. Also this kind of series are aimed at young readers.
Other thing is Isekai sometimes undermined the psychological aspects of transported between words or being reborn. It's like in one chapter they are already comfortable with that fact and even fit in. Also being physically a helpless baby with the mind of an adult must cause some change in your psyche or something (and you have to bear with it until about one year, or whenever you can talk and your physical development catch up). I might be wrong because I don't know psychology, but human mind is very fragile as far as I know.