I've not seen a homebrew that makes me want to play it more than deep blue or tv sports football. Give me a side scrolling beat 'em up like Legendary Axe II. Until then, I don't have crazy money to throw at a trinket to collect dust on my shelf just for the sake of having it.
I can relate to some extent. The thing is, indie developers have to start somewhere to get their chops up. If we care about keeping the TG16 alive, we need to support them. The less un-profitable it is for them to develop games, the more they'll make and the sooner they'll get to your side-scrolling brawlers.
While not every homebrew has been a home run, it sounds like you haven't given them a chance. Have you
played Atlantean? It's freaking awesome. Like a cross between Air Zonk and Galaga '90. IMO, it really feels like a first-party release, albeit a remake of a classic game. Pyramid Plunder is solid and almost as close. Revival Chase is interesting and multiplayer. Mysterious Song may be a Dragon Warrior clone grounded in 8-bit style, but it's a fun romp with nice visuals. Hypernova Blast and Insanity are rough around the edges, but still get play time when I'm in the mood for a simple game with solid play control. I own 25+ official titles that see way less play time than these games.
Finally, with the possible exception of Atlantean, none of these games are "crazy expensive." They're all a paltry $10-40. You can get
all three Mindrec releases for $50. The last copies of Mysterious Song went on clearance for $12.