Probably an over dramatic way of stating it, however it seem that there is a noticeable movement by developers and other platforms toward native Linux support.

The "All your games in one place" slogan does not seem true if I still need to run other platforms in order to get my games to work.
If Steam/Proton ever launched a service similar to Galaxy 2.0 then they will probably move the player base over to them.

I am not a Linux user at the moment but having recently weighed the pros and cons, I have decided to migrate myself and my whole office to Linux. I will definitely move my home PC for gaming to Linux.

I really like GOG and would prefer to use their service, but they need to see the way the wind is blowing, and at the moment it is turning in the direction of Linux.

no. the linux gamer base is less than 1%, so pretty much insignificant

galaxy 2.0 is not unique. Playnite does it for Windows, GameHub for Linux.
galaxy 2.0 just does combined library shelves. Security aspect of it (web logins) would turn away any Linux user from using it. Unless you went to Linux just to be able to share logins to your gaming accounts with no-names from github.

no, having galaxy for Linux users in a state it is now won't do much. considering small percentage of Linux user base and lack of attractiveness of galaxy 2.0 for Linux there's no way it can influence faith of galaxy 2.0 in general.