Steam is great! But so is competition, and GOG has been one of the best of them. A healthy mindset and a strong focus on their relationship to the customer puts pressure on steam to do more than the bare minimum to stay in the lead. We’re lucky in the fact that they’re both mostly good companies to their consumers.
They each have their own issues, and I do question the effectiveness of GOG’s strategy here, but GOG doing well is also good for you as a steam user!
There’s an app, and I’m sure others like it, called Tidy Panel that lets you block notifications based on the content they have. The free version let’s you block a handful, but you need premium for unlimited. For you, the free might be enough.