I'm not a huge fan of the isekai genre, but that doesn't mean I hate it either; its ubiquity is what makes me wonder why people don't just make straight up fantasy anime.
Frieren for example would be terrible if Frieren was actually some random person from earth who got sent into her setting (or, as Frieren's whole thing is outliving her comrades, her purple haired protege was the isekai'd protagonist); I understand how the isekai nature of an anime can also affect the anime, for example a character who has modern world knowledge he applies in the setting, or modern world tech, but if he just becomes a part of it, and NOTHING from his real life has any impact on the setting....then what's the point?
Overlord for example (which I didn't enjoy to be honest; I googled if he ever faces a challenge and nope, entire series and he has zero things that can challenge him) would not have been affected if he was just some lich who woke up a thousand/hundred years later.
Konosuba benefits from the isekai genre in that the isekai elements keep being relevant throughout (Spoilers:
spoiler
for example that guy who chose to reincarnate into the world with a powerful sword that Kazuma stole, or Kazuma dying and Aqua's replacement reviving him repeatedly, or that the demon lords at some point realized all their most annoying hero enemies keep starting in this one town and so decide to attack it, or that ancient scientist who turns out to be have been an isekai'd hero who creates stuff inspired by stuff he was a fan of
Most isekai animes today just seem to be wish fulfillment harem animes, which are a problem on their own as well, but they're paired with being isekais too (if you're wondering why I didn't make a thread on wish fulfillment harem animes, it's cause by and large I avoid them like the plague).
There are some interesting POST isekai stories that I found fascinating, stories where the characters came back from the isekai world and had their powers with them; in one case some of the heroes become devastatingly powerful villains who destroy entire cities, in another case it's a comedy about some guy who comes back and....could have been funnier without the ecchi/SA nonsense happening throughout.
Animes like SAO (which I didn't find interesting beyond the first story) make the other world an entirely false world and never let you forget the characters are real people who can actually die in the real world (sort of an anti-isekai genre).
In general, if they're not going to benefit from being isekai....then just make them normal fantasy. So many good fantasy animes out there that would have been hurt by making the protagonist just an isekai'd character.
I have just now had a thought that the Standard Isekai Setting allows people to write in what is de facto fanfiction-like alternate universes of the same setting, with many of the same benefits. The hard work of world-building is all done for you! The Standard Isekai Setting has an adventurer's guild where people fight monsters for money and there's a demon lord out there somewhere and there are character classes and sometimes it's a video game etc etc (all of which seems vaguely inspired by Dragon Quest to my western eyes), which allows authors to use it as a shorthand and then maybe they add twists to their ~~AU~~ original isekai story. Perhaps the main character is a vending machine, or is a sword, or has a cell phone.
Like with fanfiction, readers like the original work and so seek out variations of that work. But in this case, the setting of the SIS, rather than any particular story, is the "original work".
I also think that the SIS lends itself well to clickbait titles, which IIRC are very important on that one website where everyone posts their isekai webnovels. If you see the title "Reincarnated In Another World To End Catgirl Slavery", you know what you're going to get.
I'm fine with this concept, but it's the ubiquity that frustrates me
Definitely an aspect that could convince me to try watching it, where something different is done (not the 'being a sword' one though, instead the real world stuff being the thing)