I find `man X | grep Y` actually works OK, and the "see also" at the bottom is quite helpful for finding related information.

But if I don't already know exactly what I'm looking for, it's hard to use. It's really difficult to "learn about" how to open sockets if I can't remember sockaddr_t exact spelling or the right header to include.

On a BSD, try ‘man -Otag=l ls’ or ‘:tl’ (from less) for e.g. ls -l. This also works for larger man pages: ‘man -Otag=OCRNL termios’. More specifically, this requires the mandoc man implementation, which is also available on Linux — it’s what I prefer for all my machines.

tl;dr: it’s groff(1), not the -man and -mdoc formats, which is primitive (in this sense).