The short answer
Being great at something that doesn't matter to you is exhausting in a specific way. The skill stays sharp but the fuel runs out. You're not broken — you've just outgrown the meaning the work used to carry, and your honesty about that is the first real signal worth listening to.
You're not lazy and you're not ungrateful. What's happening is real: research on overwork consistently shows that working hard without a sense of purpose creates a particular kind of strain — different from burnout caused by too much pressure. The drive stays, the output stays, but something underneath quietly hollows out. You're describing that hollow. The competence making it worse makes complete sense — it removes your excuse to leave or to complain, and it keeps you locked in.
Marcus Aurelius asked a sharp question: what is your profession? He didn't mean your job title. He meant: what are you actually here to do? His answer was simple — to be good, to act in a way that benefits others and connects to something real. When skill and meaning split apart, you end up with craft without direction. The work becomes technically correct and personally empty. That's not a performance problem. That's a meaning problem.
This week, pick one small task you did well and ask one honest question about it: did this help anyone, in any real way? Not 'was it approved' or 'was it praised' — just, did it land somewhere useful for another person? You're not looking for a life answer. You're just looking for one thread of genuine usefulness to pull on. That thread, even a thin one, is worth finding.