I thought GOG was our lord and savior of not having proprietary launchers?
The website/distributor itself IS that way. GOG Galaxy is an optional client with several 'nice' features. I have archived all games I've purchased from them via the GOG Downloader, but use the launcher anyway for convenience (like cloud saves).
That said, they have ceased support for the GOG Downloader so I'm a little concerned about that.
So GOG is taking after Discord a bit and wants to appeal to the "No Steam, no buy" drones. Because simply being the most consumer friendly platform wasn't enough to get them noticed, but cool I guess. I opted into the beta so I can give them feedback.