I didn't downvote you, but I can only speak from personal experience that I haven't found the start screen to be any slower vs. the start menu.

None of the negatives you mention apply to my usecase (I don't typically rename shortcuts, nor did I ever use the recent files functionality etc.)

But what I do find is that the start screen is faster for opening the application I'm looking for: I'm either searching for a particular name as with the start menu, where the speed is about the same, or I'm browsing around looking for something whose name I can't remember, for which I find my groupings of smart tiles far easier to parse in a quick glance than I ever found navigating a directory structure in the start menu.

A directory tree to open applications still seems a bit like a holdover from the filesystem design, rather than an interface that's been designed for the purpose of finding the right application fastest.