@Cero90 @Otaku_Gandulf If you've been around long enough most people become jaded with the genre due to a laundry list of problems. Like...
1.
Overused gimmick and under-cooked story - this can be seen in any genre that has had a boom in popularity (mecha,magic girl, shonen). We just happen to be living in the Isekai age, it's still technically a very new genre.
2.
The plots use very generic tropes - Whether they be tropes exclusive to this genre or from others, people have seen it way too many times, and way too frequently.
3.
It's been done better - Each person will likely have an Isekai they love and it will always be a standard in which they measure new Isekai.
4.
Subject + Isekai = story - For example, I saw homeless man in Isekai and Minecraft Isekai just yesterday. People might read a chapter due to your gimmick but often times those same people find out the gimmick is all they have, leaving them with dissatisfying characters and world building, I.E. a bland or bad story.
5.
It's unnecessary - if your story is not gimmicky enough then it will lead to the question of why even be an Isekai? If your story spends maybe a chapter to have your MC give a sob story or explain why he is quirky follow by immediate death by truck-kun(a trope so overused it has a
name Manga)[Shout out to Miserys_End for the edit], thereby sending the MC to another world (maybe talk to god(dess) along the way) , and then they treat the rest of the story like it's a fantasy story with poorly explained and seldom used DND mechanics. Then you might as well scrap all that and make it a fantasy story from the start.
6.
Same setting different subject - 9 times out of ten the Isekai setting will be set in a generic medieval fantasy era. I have come across one maybe two Isekais where they took place in a space fantasy. This of course is boring and redundant to most people.
These are just the common issues I can think of off the top my head, but, personally, I don't outright hate the genre nor do I think most people do. They are just tired of it being so common and most times disappointing.