Galaxy IS garbage. But honestly, why would you want a launcher to do anything other than launch games. The whole mod support, and all the other added services are utter nonsense, games/publishers should manage that per game. Them not doing so is what creates this strange situation where the same game can't run launcher agnostic because numerous elements are 'done by Valve' or whatever other party.
See, that is the long and short of platformization. The companies that launch products on them, launch a product that 'looks' the same as it always did, but under the hood they paid others to deliver parts of it for them. So you're not buying 'the product', you're buying in to the platform. And then you're suddenly connected to a platform when all you needed was a product.
So GoG and Galaxy while being not the most optimal solution... are still the ONLY solution that releases products as feature complete things that work independently of the launcher. Realistically that's what you're expecting to get, right, when you click a buy button on any website?
Luckily in the case of Steam all you really need is a dll to circumvent the whole DRM they deploy, which is why every other pirated game is a Steam release, but still. Its not accessible unless you hack. Similarly, on Epic Games Store, their DRM is virtually nonexistant as well, but that stops abruptly when publishers start moving features to the platform, like mod support or the community elements. What we're also seeing is that publishers still deploy their own launcher behind the platform, so its clear they see a similar risk of not having full ownership/control. After all, you don't implement or pay for things twice on purpose.