Maths. It's my field of study and I'm reasonably good at it, but I'm no more able to find joy in a nice definition etc. It's just boring.
Even if I study some out-of-syllabus topic I know that is interesting, it doesn't interest me.
Is it possible to change your field of study? I was the same way with electrical engineering, I switched to comp sci and got a minor in math after I realized that a career in EE would bore me to death more than the school work did. After I switched, I actually loved (almost) all of my classes and I enjoy the work I do for my career
I feel you, I burned out heavily on maths at least twice while studying engineering. Took me years, and a bunch of watching math videos while high, to rekindle some interest.
Maybe try working backwards? Find a real world phenomenon that interests you and explore the math that models its behavior. It's a big subject with lots of variety, symbolic logic is different from DiffEq which is different from topology which is different from dozens of other subsets of mathematics. They all function differently and they can all represent different phenomena; maybe it's just the abstract nature that bores you.