Like you, I had old retired server hardware for Unraid earlier this year that I used for many years, and it worked just fine. However, I decided to modernize my setup and retire the old hardware. I gave it to an enthusiast friend of mine to do whatever he pleases with it.
I wouldn't say the hardware you have now is a complete waste. Instead, it provides a good platform for continuous learning. Is it overkill? Perhaps, but it's not necessarily a bad thing either.
In my server, I have 11 disks and one cache drive. The majority of those drives host all my media and files, while three of them are dedicated to downloads and random stuff that I don't organize too well but still keep around. It may not be the tidiest setup, but it works for me. Every six months or so, when I'm bored and want to try something new and learn, I streamline it. I also don't use parity because I like to live dangerously!