It's been a death by a thousand cuts over the years. The only reason I still had a Windows partition was to play specific games that couldn't run using Proton on Linux. The start menu's inability to be moved to the left side of the screen was the last straw for me. It sounds pedantic, but that's where I've had my start menu forever, and I'm not about to change yet another thing in my workflow.

At this point, if a game won't run under Proton because of an intrusive rootkit, I'd simply rather not play it.

Edit: I specifically mean the start bar vertically aligned on the left side of the screen, with the start button in the top-left corner, not at the bottom-left.