There is a remarkably active Amiga fan scene that continues to use these OSes for "real" and develop new applications and games. Frankly, it's amazing; random examples: https://amitopia.com/muimapparium-0-7-for-amigaos/ , https://amitopia.com/inviyya-shooter-for-amiga-500-in-develo... .

I've fantasized about doing it myself on more than one occasion. The price of new Amiga hardware sort of puts me off, but it's not outside the range I could afford. Unfortunately, I don't quite have the time right now (and, for once in my life, it's not a silly "i don't have time" excuse), so I'm watching it from afar.