I built a Mini-ITX PC in 2018 to watch videos and practice Python programming. Fast forward 4 years, I have replaced the original case with a 4000D and switched in a 6700 XT to handle higher end games. Also I brought the RAM total to 32GB since I found websites were eating up more and more memory. The Ryzen 5 2600 can still handle everything I throw at it so I'll wait a bit before upgrading to a new processor (fortunately AMD confirmed AM4 for the foreseeable future).
The unsung hero of the machine is the modular power supply. It's much cleaner now that I can attach and detach cables as needed. I used to have a semi-modular power supply, and while it wasn't bad it never seemed neat enough.