@matigo Something I've observed to varying extents across UI design is the tendency to assume that things will happen immediately.
In this case I'd downloaded a video from Twitch — 4GB — and the transfer was not instantaneous (and no one would expect it to be). Some UI confirmation was essential.
It's increasingly not an entirely unfair assumption to make given the progress in hardware and software — a great deal of videos would transfer near-instantly — but it's a dangerous one, in my opinion, and I would happily not go in that direction.
That said, my general perspective on (non-touch) UI design is that we peaked somewhere around the Windows 2000 era and that flat design has been a curse all around.