Well, pipewire is being used by gamescope kwin weston pipewire-devel obs-studio krfb gnome-remote-desktop xdg-desktop-portal mutter wireplumber plasma-workspace telegram and pipewire-32bit is used by steam.
So if you use the Solus MATE edition, and no flatpaks, no Telegram, no Steam, no OBS, etc. etc. it might be possible to get by without it (not really sure if there isn't a hidden dependency somewhere in there though). But I don't really see a strong reason for trying to do so. If it's already installed on your system, chances are you're going to need it.
