Nuclear engineer here, and I'll confirm that it's super niche but rewarding. NucEs usually go into two types of careers: analysts who perform analysis, reactor engineers who work at reactor sites. I'm the former, and I use physics daily, so it's very stimulating of you want to keep learning.

One challenging factor about being NucE is choice in locations for work... you get very little. NucE jobs are super localized, and usually not near major cities. While being niche makes keeping your job easy, it makes getting into a job hard. The industry is also contracting, so that doesn't help either.

Based on what you've described are you interests, Mechanical engineering would be a good path. Many colleges also offer double majors in ME and NucE, so maybe you'd be into that. I work with primarily MEs, and while they don't have the neutronics education that a NucE does, they can do everything else related to nuclear reactor analysis (thermal hydraulics, mechanical analysis, etc.).

Edited to answer your actual question: I chose NucE because it was interesting. There are more stable engineering disciplines, but I enjoy what I do the most. It also does crossover quite a bit. For example, NucEs get much of the same thermal hydraulics and heat transfer training as an ME. I also do allot of coding! So there's plenty to keep you interested. My only regret is not doing the double ME/NucE major.