Frankly, it annoys me more that for all the isekai out there, basically all of them are the same cut & copy fantasy European-ish setting. Why not more sci-fi isekai? Or as you pointed out, an actual alien world isekai.
There's no isekais out there, as far as I know, that are anything like the game Another World.
It's the safest bet, that's really all it is. Publish what's hot or easy and avoid what could be considered uncertain.
Remember: Isekai is so synonymous with the monotonous, repeated structure that you'd be forgiven for forgetting that there was a time where they DIDN'T reference the fact that Isekai exists as a genre in their own stories and lines like "Is this what you call another world!?" and "Cheat skills" weren't a thing.
This means they're easy to write and sell off because most of the work is already done for you by the genre itself. You don't have to create character development, drama, conflict or even establish a personality because the genre doesn't need them. You just need some random "average" guy and a bunch of breasts and your job as an author is done.
It doesn't matter that the average person doesn't know basic infrastructure, economics, engineering, agriculture or anything required to build a functioning society, the character can and no one reading will bat an eye, take your check and go home for the day.
Even if your work gets cancelled, it doesn't matter because you can literally do it all over again with some tweaks here and there and still move a bunch of copies until the day that gets cancelled and then you can do it again and so on. Simple, repeatable, effective, efficient, profitable. It's the dream scenario for publishers and would-be authors alike. So the stories that actually try something different will inevitably be few and far between because that's either not what the publisher is looking or the author just isn't interested in writing outside the box.