As someone who has been in it full time I can assure you that I've played with more than a few part-time musicians ("hobbyist" musician as you like to call them) that can run circles around quite a few full-time, so called "professionals" (in every single department you mention). They could very well be earning living as a musician, but they just chose to make the bulk of their money doing something else. Just because you do something on a regular basis, doesn't instantly put you at 'another level' (unless you want to factor in struggle in the case of a musician). Some people are just born natural performers. Also, I've know some pretty underwhelming full time performers that get a lot of gigs, but not because of their music and musicianship, but rather their persistence and craftiness in getting gigs. In short, not all "pros" and "hobbyists" are created equal.
This is true, there are great “hobbyists” out there. But that doesn’t mean that pros suck. While there is overlap, the average level of pros is higher than the average level of hobbyists. I would much rather do music for fun than rely on it for my livelihood. To those that are making it happen, kudos.