Almost every time I see a halfway polished “solo developer” game, they did not do all the work themselves. Especially, they usually hire out the music, maybe other sounds, and much of the artwork. Sometimes they also have freelancers doing marketing and such. Sometimes even some paid help writing the software.

I highlight this not to bring those developers down, but because I think it’s important people understand how these things actually come to be, so they aren’t discouraged to try themselves by thinking they ought to actually be doing 100% of the work solo. That’s pretty rare.