Firefox gets in the way while downloading files [closed]

After a recent update, Firefox introduced some sort of a download tool which manages large file download and silently reconnects if connection fails. After the file download is complete, it pops up the file save dialog and prompts user for a filename. I think it is obvious that downloads take long time to finish - therefore, user is guaranteed to begin doing other tasks instead of just waiting. So, while he is doing other tasks, Firefox simply interrupts him, takes over the window focus and pops up a dialog - with a text field immediately focused. Of course, 99.9999% of the time the user types in his keyboard commands into the filename, effectively erasing the original filename for the downloaded file, messing his current work and experiencing stressful situation.
Question: why are there still such trivial user experience fails in 2021?