are there any isekai stuff that
I don't know any isekai anime but here are a few manga:
(I'm too lazy to add more but if you'd like I can rec some more later (´︶`) )
When the Villainess is in Love
Who Made Me a Princess
Villains Are Destined to Die
Yongwangnimui Syepeuga Doeeotseumnida
My Life as an Internet Novel
The Devil is a PartTimer
there is some fight scenes, but for the most part, its slice of life.
Ive Been Killing Slimes for 300 Years and Maxed Out My Level
decent fluffy slice of life
My Next Life as a Villainess All Routes Lead to Doom
ok so this is a complete harem, but its a female mc with both male and female harem.
Who Made Me a Princess
manhwa^
This one goes against your first criteria, but it's still very fun.
DRIFTERS
This one has a little bit of harem stuff, but it takes a very small part in the show. It still has plenty of other enjoyable aspects.
Overlord
And then theres this one which fits all your criteria, and I think is a very good isekai overall. Looking at your list, I think you might like it.
Ima Soko ni Iru Boku
Grimgar of Fantasy and Ash
Ive Been Killing Slimes for 300 Years and Maxed Out My Level
The Devil is a PartTimer
I would involve Tanya too,
Saga of Tanya the Evil
Has absolutely zero ecchi scenes and no harem but has a lot of fighting.
...ascendance of a bookworm fits the bill
uh... Didnt I Say to Make My Abilities Average in the Next Life (contains a decent amount of fighting scenes, but it's not about saving the world) and Kuma Kuma Kuma Bear count, I think. Any other similar show also counts, but most of them feel fairly harem-y so you need ones with a female protag, which is uncommon.
Log Horizon is excellent, it has fight scenes and has the very very basic elements of a harem, but it's mostly about exploring what it would actually be like in an MMO. It's very long, and a bit slow, but seeing as you liked Katanagatari, I think you'd also really enjoy this.