Modern storage is at least hundreds of time bigger than when shared libraries were common to save space. Every single executable having its own copy of GNU C Library isn't a big deal.
https://blogs.gnome.org/alexl/2017/10/02/on-application-size...
I can't speak for the others, but Flatpak is a layered solution, so files are deduped and shared across the layers (runtimes, applications) that need them.