TFTP is probably the exception to that rule. All the other protocols started out easily enough and added more and more cruft. TFTP stayed the way it's always been - minimalist, terrifyingly awful at most things, handy for a few corner cases. If you know when to use it and when to use something like SCP, you're golden.

If TFTP had gone the way of SNMP, we'd have 'tftp <src> <dest> --proto tcp --tls --retries 8 --log-type json' or some horrendous mess like that.