I get where the "second-class customer" feeling is coming from, but in reality the choice is probably often between having the game without Galaxy features, or not on GOG at all. The customer base here is still much, much smaller than on Steam. And even something seemingly simple like achievements is never to be underestimated. Some developer needs to have read up on and dealt with the API, do a robust multi-client implementation, have it properly tested… that's going to be a few days already, plus you burden yourself with the obligation of keeping it updated with any new clients and APIs. And programmer hours are not cheap. That additional cost will be very directly compared with how much the publisher expects to make from GOG sales. I'm neither fiercly pro- nor anti-achievement, I just see the publisher's side of deciding case-by-case where they want to spend that effort. Given limited resources, I'd rather they focus on delivering patches at the same time.
The calls are probably relatively non-invasive, but… we all know that developers always stick to the rules and never stray from the officially documented way of doing things, right? ;D I do agree though that, should it ever break, a Galaxy dependency would be relatively easily patched out compared to other stuff. A simple wrapper that accepts the right calls and does nothing would probably do the trick. I also think that GOG developers probably care about stuff like that and try to prevent any unnecessary interdependencies.
About the game, the trailer immediately brought back memories of Microsoft Monster Truck Madness 1 and 2. I still have those discs somewhere, the second one I believe is an OEM copy that came with my awesome SideWinder Force Feedback wheel!
https://www.amazon.com/Microsoft-Sidewinder-Force-Feedback-Wheel/dp/B00000JDG9 That thing was awesome and probably still is somewhere in my parents' basement. Just seeing the picture I hear the sound of the FF motors in my ears =D
Edit: Hey hey, wouldn't you know it! I'm surprised no one pointed it out yet in this thread: developed by Rainbow Studios, creators not of the original Monster Truck Madness, but Motocross Madness (which later turned into the MX vs. ATV series). Might be good to know, I also remember a few mediocre MTM knockoffs over the years but Rainbow Studios generally know a thing or two about good racing games.
By the way… I rarely downvote posts I disagree with, but I quite often downvote those who dismiss the motives of expected downvoters in advance ;)