You shouldn't write off the isekai genre so quickly ( I mean technically Digimon is an isekai so take from that what you will.) I've found while yes there is a fair bit of garbage, a lot of Isekai have a lot of freedom to make really interesting worlds and write some really interesting characters. Take it from someone whose watched a fair bit of isekai. I personally really enjoy Isekai for providing me with some of the most lavish, large scope world building since One Piece. It even got me into reading the light novels for some of the series for the extra detail.
Here are a list of some of my recommended Isekai.
1. Overlord: A really interesting premise where the main character is a company worker playing a maxed out amoral Undead King/Guild Leader who is teleported into a different albeit real world from his original game world when the servers shut down. In his original game world, his guild was upper mid but in this new world, they are the absolute strongest force in existence. The worldbuilding and characterization in this series is top notch, the interest coming from how this massively powerful organization meticulously goes through the process of world domination. The pacing is a bit slow and the third season is notorious for bad cgi but I find the world and characters worth the investment and it even got me to read the light novels which are even better.
2. Konosuba: Hilariously funny isekai with a super weak protagonist stuck with the worst class of Adventurer, an all rounder can do anything but good at nothing jack of all trades class. He's also stuck with a trio of pretty girls who while fairy powerful in their specialized fields are the most dysfunctional, idiosyncratic weirdos that no other party wants to deal with it. Think of it as an isekai where the protagonist is Usopp making the most of the cards he's dealt with. It's really funny, subversive of many isekai tropes and has great animation. Still waiting for that third season…
3. Re:Zero: A bit controversial, the premise is about a normal guy sent to an isekai world whose only power is if he dies, he's reset to a prior checkpoint and has to try again except it comes with all the physical and emotional horrors of dying. Think of it as a far less funny Groundhog's day. I say a bit controversial because while the world is super fascinating and has some of the best characterization I've ever seen, my god is the pacing glacial and it takes so long to get to the point, it almost comes off as misery porn. Even the way the dialogue is written and paced feels like the lightnovel being transcribed instead of pacing it in a way that more naturally fits an television. I do think the investment is worth it in the end but this anime comes with a caveat.
4. Saga of Tanya the Evil: If war politics and complex war strategy is your thing, you'll enjoy this a lot. If not, I think the protagonist is strong enough to carry it. The world is basically a fake world war one but with magic and you're on the side of fake Prussia. The protagonist is a former business executive turned little anime girl who is trying her goddamn best to play the odds and secure herself a safe, comfy position away from the frontlines. The sardonic gallows humor is my cup of tea but it can be quite heavy for people who prefer something more light.
5. Ascendance of a Bookworm: Lovely, lovely series. A girl who loves reading books dies and is transported to a mid 16th century world where books don't exist yet except for the very rich. To top it off, she's reincarnated as a very sickly girl in a poor but loving family with very little time to live. She has to use her intelligence and 20th century smarts to turn around her situation and finally read her books. The characters are fantastic, the world while not that interesting in scope, is very intricate in how the characters of different social class interact with each other, it's just really good at making you feel like these are real people living their normal day to day lives.
6. No Game No Life: By far the flashiest series on this list. Two genius siblings are transported into a world of rivaling kingdoms of various races with the twist that these kingdoms can only compete and win territories through games. Our duo are with the Human Kingdom, the weakest kingdom with no ability to use magic and they have to use their intelligence to turn the situation around to overcome their superior rivals. It has the trope of having your super smart protagonists that can do anything but given they're fighting rivals who can literally cheat with magic in their games, I think it evens out. I personally adore the breakneck pacing and over the top animation in this series but it might be too much for other people. Also this world of various races competing for supremacy is really fascinating and I wish we got more detail about them. Doesn't help that it's too short with only 12 episodes since 2014 but a movie came out recently so maybe the series will finally make a comeback, maybe? Or I could always fork money for the light novels I guess.