I remember we made a switch to redis because java's memcached library was unmaintained. I made I joke that it's just feature-complete and cannot be improved upon, people chuckled, but we still did the switch.
Hell, the main feature I needed (bulk CAS get) didn't even require the meta protocol or recent memcached features - spymemcached just never bothered to implement it. I ended up abandoning the change I was working on, because the upstream never looked at my PR and it wasn't worth forking over (bigco bureaucracy etc).
There are also quite a few legitimate bugs open for years that haven't had so much as a comment from maintainers.