I've tried a few eps of Iseleve and while I like the basic premise of two worlds, a down-to-earth nice guy inheriting a legacy, rpg/fantasy elements, etc and harem/ecchi stuff doesn't bother me at all...
The part I can't get into is the overwhelming OP-ness of it. No, I think I'm doing a bad job describing what it is that is bothering me... I have watched and liked plenty of things with OP characters like One Punch Man, Mob Psycho, (old) Bleach and read a fair number of light novels with OP chars like Mushoku Tensei, Everyone Else Is a Returnee (Korean), Stop! - Friendly Fire (Korean), as well as plenty of wuxia/xianxia stuff...
I think what I don't like is that is feels like the MC is literally handed everything and there is no challenge whatsoever; for me it feels a bit like a story-on-rails feeling and I don't feel really connected to any of the characters, as if they are just cookie-cutter templates with no depth or personality.
I think there have been a few anime over the last couple of years with a similar feel (there was one about a Demon King reincarnated at a school or something I can't remember the name... maybe it was this one?) and a few other isekai's.
So for you guys that like this kind of thing - I'm sorry if I'm coming off as a bit negative towards it, I honestly am not trying to shit in your cup of tea - but any insight into the appeal would be appreciated.
I think I can help but it will take more than just words. It will take a demonstration and I will need your help to convince your gf.
But you can say that cigarettes make you better in bed. If you gf is hot and you can convince her, I'm willing to sleep with her and do a bad job to help you look good. After a few sessions to rule out one-off performances and so on, I am confident she'll be convinced.