c++20's u8strings took a giant steaming dump on a number of existing projects, to the point that compiler flags had to be introduced to disable the feature just so c++20 would work with existing codebases. Granted that's utf-8 (not the same thing as unicode, as mentioned) but it's there.

And yet, unicode support is still abysmal throughout the standard library. I don't disagree though.

Things like char32_t, std::u32string for storing UTF-32 characters.