You already can't fit the entire standard library on many microcontrollers people use C++ on (hell, you can't even fit the entire C standard library on most of

You already can't fit the entire standard library on many microcontrollers people use C++ on (hell, you can't even fit the entire C standard library on most of the micros I use, and they aren't exactly the smallest ones on the market). It still works because if you use the right compiler and linker options then you will only include the parts of the standard library that you actually use.