Launching a game means that the entire Steam Window fades and it will become entirely unusable until the game starts. That is not a separate startup window, thats just an embedded element inside the main one. If you accidentally click outside, the game startup gets canceled.
It is a bit more than mildly frustrating when Im waiting on the Vulkan shaders for BFV for like half an hour to process.
Why would you need to browse steam while you’re launching a game? Is your object permanace so fucked that you can’t wait for shaders to compile?
Compiling shaders can take a long time for some games though, MCC took about 15 minutes for me. No reason to unnecessarily lock the UI from UX perspective anyways imo