My nickname for “Big Sur” is “Big Slow”.
Aside from the Finder failing to open the Preview and MS Word apps when double-clicking Preview and MS Word file icons after startup, my biggest beef with “Big Slow” is slowness of the Finder.
I have several folder aliases in my dock. When I click one of them, the folder’s files and sub-folders are displayed. When I hover over one of these sub-folders, the Finder is extremely slow to display that sub-folder’s contents. This continues down through the folder hierarchy.
This extreme slowness did not occur in Catalina, which displayed sub-folder’s contents virtually instantaneously.
Reinstalling Big Sur did not fix this issue.
I’m using a 27-inch Retina iMac Late 2015 with 24 GB of RAM and 2 TB of storage.