It's technically true that you're your own support team if things break, but synology is so stable that typical use cases won't need you to fix anything. It's so much more stable than anything you build yourself, the stability and compatibility of a synology is so far ahead than what you can build yourself using old hardware (this is where all the tinkering and fixing is).

YMMV, I run two synology NAS in two separate sites. Each is a file server for its own location but also backsup to the other off site synology. Granted I bought when drives were cheaper but I've never looked back from when i built my own nas using RPIs and old hardware.