3D level design is extremely difficult and time consuming.

Every time I tried level design I ended up abandoning the level the next day. It takes me about 6 hours to greybox a giant area, something like a level just outside the castle walls with two branching paths. Add in some elevation and shortcuts and then I feel like it's done. When I open the level the next day, I realize how much work there is left because there's no lighting, enemy placements, or textures placed on these meshes and then I quit.

Even for something like a combat arena, I really struggle in making something interesting because my own standards are very high for 3D levels. As someone who loves 3D action games with exploration like the souls series, I don't think I'm capable of making a level worthwhile without investing years into it and I find it very unenjoyable past greyboxing.

I think it takes a special kind of skill set to be able to make levels because it's not as instantly rewarding as something like system implementation, enemy design, or art.