They keep releasing more and more generic isekai because it's the simplest thing there is, it's what's most consumed in the East. It's like with RomCom, most are generic school romance stories with fanservice and generic clichés, and that's what people consume the most these days. The era of original and engaging anime is over, or at least that's the impression it gives. Because anime worth watching is still being produced, anime that are different and unique in their style. It's just that they aren't promoted or don't have the fame that isekai or rom-coms or action and fantasy anime have.

Your problem was that you started by watching the worst isekai anime out there, and that gave you a bad impression of them. But the fact that there are good isekai anime is undeniable. That's why I mention Re:Zero, because it's a very different isekai from most, one that revolutionized the genre. From its protagonist to its story and the construction of its world and characters, it's all completely insane. It blends comedy with action, fantasy, drama, psychological suspense, horror, mystery and even science fiction with the theme of parallel worlds.

When you watch Re:Zero you will know the minimum quality and originality you look for in an isekai. You won't regret it, really.