macOS Catalina: Opening simultaneously multiple folders very slow (when compared to Mac OS X Leopard)

In macOS Catalina, always in List View, when I select say 10 folders and press ctrl-o to open them, it takes approximately 10 seconds to open them all. Roughly 1 folder per second, whatever the folder and whatever its content. Closing them with cmd-alt-w is almost instantaneous though. When I compare that to say Mac OS X Leopard, the same quantity of folders open (and close) almost instantaneously. I searched the web and found nothing regarding this matter. Any ideas on how to have on macOS Catalina a speed similar to the one of Mac OS X Leopard?