GC was removed from the C++ standard in C++23 because all the compilers were like "hell no" and it was an optional feature so they could get away with not adding it. So this optional feature never actually existed and they removed it in later standards.
The C++ standard has never included a garbage collector. It only provided mechanisms intended to facilitate the implementation of a GC, but they were useless.
There are ways to do GC without language support. They are harder, but have been around in various forms for decades. They have never caught on though.