These are all valid points - in fact I have my own (almost-but-not-quite-finished) semi-retrocomputing project too: a cross-platform MOD (the old Amiga music format) player written in Go (https://github.com/nieware/go-modplayer). Which may not be useful to a lot of people, but at least it was useful for me getting better at Go. That's not to say all of the things I do in my spare time are useful though - most of the time I end up playing games or browsing HN, so even less useful than reimplementing version management for an ancient OS.