It depends on how many shell extensions you have installed. How something so basic can drag a supercomputer to its knees is puzzling but MS never fails to deliver.
Its a disease all over software engineering. We add just enough layers of abstraction, but no more, to make it about ten times slower than a Commodore 64. The excuse is that it's to avoid having to think end-to-end as one human can't possibly think end-to-end these days. The reality is the reason they can't is because of all these useless indirection layers in the middle and if those were deleted, they could.
One wonders if it would be possible to invoke those extensions asynchronously and put a little "loading" icon where any new shell items might appear. Or have a hard 2s timeout after which any latecomers get shoved behind another layer of menus.
If you turn off animations they ARE loading the menu asynchronously. You'll see a basic menu with the extensions added on as the menu continues to grow and reflow. It's worse if you right click on a file. It also DOES use "loading" placeholder text
That's total BS, unless it's MS' own code in those extensions. Very typical of them to blame others when it's their own shit code that's causing the problem.
As the other comment here notes, shell extensions have been around for a long time, and have never been a problem on older versions of Windows running on hardware that's much slower than what's available today.
At least on Windows 10, which I still run, pretty much all of the "explorer is slow" issues are caused by shell extensions.
The problem is a lot of the times they make poor assumptions (like "if a process is running it'll respond instantly") and honestly the tools that exist for determining what is at fault are... well effectively nonexistent[1]. This goes even for 1st party shell extensions. Part of the problem is these almost inherently violate what I consider one of the golden rules of GUI programming (don't block the UI thread) and there's a lot of historical reason for this, but it is often the cause of stuff like "explorer.exe uses 100% CPU" or "right-click takes 30 seconds"
[1]: There's a SuperUser post in which the recommendation is effectively: manually binary search for culprit shell extensions yourself (https://superuser.com/a/577935/312312).
