The only better alternative (for me) would be a bunch of DRM free stores feeding their catalogues to an open source front-end that has everything that Steam already does.

Like Heroic, Lutris, Playnite, etc. But way more developed features and with official vendor support and a built-in unified store that supports all catalogues in the same view, like a federated marketplace.

That would be the only thing capable of moving me away from Steam completely.