The Isekai genre goes deep,
very very deep. Anime adaptations only really cover the often good and/or mainstream series.
If you start digging into Isekai manga, there at least one order of magnitude more works to choose from. Then if you look into light novels, there is even more stuff, again with just a fraction getting manga adaptations.
But the real breath of Isekai are web novels - that's where most of the current hit novels started, on websites like "I'll become a novelist" (https://syosetu.com/) where people just type away their fantasies with minimal friction, one chapter at a time and often with lots of direct feedback from the community.
That can result in even more original/crazy ideas being explored, such as:
- What if you were transported to a fantasy world with your solar powered camping vehicle ? (Himekishi to Camping Car)
- What if you became your game character in a fantasy world that has a different gender (female) and is a total glass cannon ? (Alice Tale)
- Whats more fun than raiding dungeons ? Running them! (Lazy Dungeon Master)
- What if there is stable gateway between the other and the modern world and you can go back and forth ? (quite a few series actually, even some mainstream ones like Gate or Isekai Shokudo)
- Fantasy is nice but steampunk and heavy industry is even better! There are quite a few rather non-mainstream series that introduce robots and guns into an Isekai setting. Yet there are others that set out to industrialize the whole thing as including building stuff like railroads.
- What if magic was just a foreign language or alphabet the locals aren't good at but you are, as it's your native language ?
- What if you are the only one who can see the GUI in an Isekai world ? Nothing better than meeting a famous aristocrat with "class: vampire" blinking above his head telling you about mysterious kidnapping cases in the vicinity. Or "goblin shaman [invisible]" floating in the air of dark cave. (Skill Takers World Domination")
- What if due to some mistake no one person gets reincarnated as a son of poor aristocrat but 3 - a high school student, a salaryman and Nobunaga ?
- What if you actually got reincarnated to the buggy mess of an MMO you helped to develop (Death March) ?
- What if a modern Aegis cruiser or even the full Japanese archipelago (including some disputed islands, no less ;-) ) gets transported to an Isekai ?
Really the possibilities are endless. There is definitely a lot of repetition and series that frankly are not any good (especially between web novels, thanks to the same zero entry barriers that enable so much creativity in the first place) but there are many gems to be found if you search a bit. :)