It's no more egregious than requiring cmake or autotools.
And like I said, many Linux systems (and almost any used as a developers machine) will have Python installed by default.
And the simplicity of meson's build files far outweighs any issues installing it.
Distributing binaries outside of package managers is a) a rarity in the Linux world, and b) not in keeping with the open source philosophy. Requiring end users to have python so they can compile a c/c++ application will never make sense for a large portion of the user base build systems target.