Wishbone: You are completely misunderstanding his issue. He doesn't want Steam features, and he certainly does want GOG to compete with Steam.
Here is the issue: Before Galaxy launched, GOG explicitly said that Galaxy's multiplayer framework would be able to connect with Steam's, so that if you had a game on GOG and your friend had the same game on Steam, you could still play multiplayer together.
Yet, e.g. PookaMustard didn't understand the OP similarly as you, but was suggesting he wanted clientless(?) multiplayer instead.
The OP said he didn't want multiplayer that requires "Galaxy", but he didn't make clear if he had an issue with having to run the Galaxy
client in order to access the multiplayer part, or being restricted to play only with other GOG players (ie. being locked to the GOG
userbase).
The "B)" part suggested he had more issue with the latter one, but in that case his blabbing about "DRM-free" didn't make any sense at all, as being able to play with Steam users has absolutely nothing to do with the DRM-freeness of the game. That part actually veers the meaning of the OP that his issue was really with the client, not so much the userbase/service.
His initial message was just quite confusing and contradictory, that's why I asked what exactly is he demanding from GOG. Not to sell the game on GOG at all, if the developer will not implement crossplay?
Wishbone: The logical conclusion to draw from this is, if you enjoy multiplayer, don't buy your games on GOG, because you will cut yourself off from playing with at least 90% of the player base.
May be. Then again, there are other PC multiplayer services which to my knowledge are not connected to Steam multiplayer either, e.g. EA Origin and UPlay. So maybe GOG should follow their way and allow multiplayer games on GOG only if the multiplayer is GOG-only?