I had a similar start to my cooking as you, not really learning how to cook until after I left home and much of it being by trial and error. Thankfully I've got a pretty solid stomach and a good ability to eat a variety of tastes. My ex used to comment that "the mad scientist is in the kitchen making brown again" as I had a habit of everything I seemed to make for snacks turning out to be some shade of brown (and I'm a scientist, and kind of crazy, but also 'lets see how this works' kind of thing)

Regarding the contests, I have no issue with the organiser choosing them to be open to everyone, open to < select descriptive group> (such as non-professionals), having separate prizes for different categories, declining entry from past winners for x time, or pretty much whatever rules and guidelines they want, as they're the ones doing the administration and running the contest.

I also don't think it will damage the community to have 2 categories (or more). If it encourages more entrants, then the prizes can also (likely) be larger, or more spread out. I know there have been many contests I've not entered (or even considered past that "oh that's interesting" because of a complete lack of even vague possibility that I'd place. It's not about the $$$ (though they're nice), but about being competitive. If I'm up against professional cooks with years of experience, there's no hope. If I'm against only home cooks, then there's a bit more chance of getting some recognition and mentions in more than just the entry post.

In the end I guess it's about why each person enters a contest. I'd suspect most people enter things because they might win, and because what you need to do along the way is fun.