Like an ancient compiler that’s also deprecated...?
libtool isn't primarily about portability across compilers; libtool is about portability across linkers and library formats, from the days when there were many systems with deficient library support. It's not unreasonable to assume a modern linker, and modern library support.
People still use macOS, which is the main reason I see "please add libtool support" these days.
It's possible to handle libraries on macOS without libtool.