On my work machine (approx 4 years old, Win10) and home machine (mostly 2 years old, graphics card, a 1060/6GB is more elderly, Win10) both take most of a second to bring up a fresh Explorer window, timing by eye from Win+E to the whole UI being present. It seems far more variable (sometimes feeling quicker, sometimes taking a couple of seconds) on my laptop (<1 year old, i5 CPU 16G RAM, Win11). All are using decently speedy SSD drives.

Several seconds sounds like an exaggeration, but it never seems anything but sluggish to me.

One UX delay that irritates me is the time it often takes between hitting Win+R and the run dialogue finally being ready for input. Regularly the first few characters of what I type after that ends up going to the app that originally had focus. That used to be instant, on much older kit.

Several seconds is not an exaggeration. The window appears quickly enough, but then spins for several seconds (there's a progress bar in the path field) before showing any file. Win11 personal, on a brand new, middle-of-the-road desktop.

Have you tried opening some files over the network, then coming back to the explorer? It'll insist on showing those files in the Recents screen. Except it actually tries to touch them or something. Which, when I'm not at work anymore, takes forever waiting for a timeout. Hell, even at work it sometimes takes a while, while doing the AD handshake or whatever it is that it does instead of letting me use the freaking explorer.

I don't use Windows often enough to go out of my way to customize it, plus I know that the next update will probably undo everything anyway, but now I have to wait around multiple seconds for it to realize the files are not there. And it won't even remember it from one instance of explorer to the next, or try to check on those files without blocking the entire app's UI.

This shitshow also happens in the open / save as dialogs when called from other apps.

Yes, this matches my experience -- I assumed it was something to do with waiting for cloud stuff, but haven't dug too deep.