if you’re looking for something for desktop, systemd-analyze is quite nice. no automated fixes, but helps with finding the problems (biggest wins for me are normally things like waiting on secondary drives, or units waiting on network when they don’t need it, etc). the arch wiki page has some general advice

vaultwarden is already reasonably mature for server

that Google/Oracle lawsuit settled pretty clearly that apis can be copied and reimplemented freely. this is just that but automated