Valve is a much, much bigger company than GoG, plus Valve's Linux strategy is really a "have our own console on the cheap" strategy.

But yeah, GoG should be doing more for gaming on Linux, maybe not as much as Valve but proportionally so. At the moment they're doing almost nothing at all: they have Linux offline installers available for games which do support Linux directly, but that's it.

So whilst I find it unrealistic to expect that GoG should be contributing to gaming on Linux as much as Valve, I do agree they should be doing more.

PS: Mind you, I'm not trying to make the case that GoG is perfect and Steam is shit, I'm trying to make the case that open and flexible to use is better than closed and tightly integrated with a specific store, which is why I generally prefer GoG with their offline installers, as well as Lutris + Wine (quite independently of GoG) and would be happy enough even if Lutris had no GoG integration since long before moving my gaming rig to Linux I had the habit of downloading and using the offline installers and did not at all use GoG Galaxy.

If there's one thing that 30 years of being a Software Engineer have taught me is that you want your system to be as decoupled as possible from any business, because even if they are nice at the moment that's no guarantee that at a later date they won't leverage people having their systems integrated with theirs to take advantage of their customers (the phenomenon of enshittification being a good example of that).