There are plenty of things between C++11 and C++23 that have been removed and hence won't compile:

Implicit capture of this in lambdas by copy.

std::iterator removed.

std::uncaught_exception() removed.

throw () exception specification removed.

std::strstream, std::istrstream, and std::ostrstream removed.

std::random_shuffle removed.

std::mem_fun and std::mem_fun_ref, std::bind1st and std::bind2nd removed.

There are numerous other things as well, but this is just off the top of my head.

None of those things I've never used. Many of those are in bad practice for C++11.