They aren't even reliably committed to no DRM. They frequently sell games that require GOG Galaxy accounts to access certain content(online/multiplayer functionality, DLC packs). GOG has explicitly gone on record saying that these forms of DRM are acceptable, despite running a store for years without them.

And preservation of old games(at least how they are doing it) is an inherently unprofitable service. Them preserving games that they don't even have the licensed right to sell is one of the dumbest decisions they have made so far. Most of their older releases have just been grabbing a bunch of existing fan patches into a more polished installer; these sorts of tasks will always end up in the hands of hobbyists who would do this work without being paid.

I feel like at this point, you have to focus on individual developers/publishers if you want to properly support DRM free releases. Having brand loyalty to GOG will get you nothing.