Hot take. There is nothing wrong with the Isekai genre. The problem is that authors have no creativity to make great isekai stuff.
For example, imagine a dude that is lured into another world by promises of being an OP caster, only to find himself in Athas—Dark Sun, powerful, yes, but equivalent to a 12th~15th level preserver or psionicist in a brutal world ruled by sorcerer kings. All epic levels. Or persecuted by the Inquisition in Warhammer 40k as a Unsanctioned Alpha Psyker. In a dead world setting. In a Midnight setting(think Lotr if Sauron wins). In a Weird West setting, where magic is hated, no matter how powerful he is, a Sharps Rifle in .50-90 can put a hole in him from a half mile away.
The problem of Isekai is that you have the Kirito tier Generi-kun with sword of fire magic saving the world in over 90% of the Isekais. There are good Isekais. For example, Drifters, instead of the teenager going to other world, is importal historical figures. Which include WW2 pilots, Oda Nobunaga, etc. Or Kono Suba. A comedy. Or Tanya the Evil. I like this Isekais. But I hate Smartphone isekai.