I also don't care if something is fashionable as such. I mean don't get me wrong, I'd feel weird in boot cut jeans, but I wouldn't wear something specifically because it was fashionable.
If it looks good and feels right, then wear it.
With leather leggings, I like rib knit jumpers, Hobbs do some great ones, they look chunky but feel thin and are flattering, or a polo neck, some nice chunky heeled suede ankle boots. Something like a grey slouchy cashmere knit can also look good. Depends on how long you want it.
I think you need to pretty much keep it elegant, or go super casual, trainers, biker boots, kind of thing, to avoid the whole "I'm well kinky me"vibe. 🤣