The end result needs to be a shared library. To prevent the need of those shared libraries you would need to rebuild every application that uses
ffmpeg (including firefox and maybe that doesn’t even like a static version).
If you statically link a shared library, you build the library’s dependencies into it. Given the only soname likely to change is
libva.so.2 (and not very often) this is not of great benefit and you would need to build the static library for libva to statically link it in (so more work).
Realistically, the only way to avoid this build would be if someone distributed the libs created from following these instructions with a matching version to what is in CL. This would still need to be manually updated from time to time from both users and distributor to get updates matching new versions in CL (I think MPV requires the same version of ffmpeg that MPV was built with, so rebuilt every version update).
The build really doesn’t take that long, but it could possibly be cut down somewhat by only building exactly what’s needed.