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.
Let’s not forget that pressing the back arrow button on the workshop kicks you back to the main workshop page, resetting all your filters, searches or visited pages. Its absolute ass.