Had the same issue with slow file explorer in Windows 10. A couple of things helped a bit, such as disabling "Show recently used files" and "Show frequently used folders". I also cleaned up the Quick access list. For some reason if you have a network share there it makes browsing local dirs slower, go figure. It's still not instant but a lot faster than the 3+ second delay.

I tried OneCommander and they're super fast, so it's not something slowing down disk IO, it's purely File Explorer.

Now I'm still struggling with closing chrome tabs being super slow sometimes.