Szenario: DO 12.22 x64, Windows 10
In a network share there is a folder with ~ 16.000 files. Displaying the file list without icons (Preferences - File display modes - details - display icons off) takes ~ 2 seconds in Details mode. Setting display icons on, it takes ~ 18 seconds. Even worse, display mode "Small Icons" takes ~ 2 minutes to display the folder.
Windows file explorer is instantaneous in all modes.
Using Process Explorer, there is no recognizable increase in CPU time, disk or network traffic while DO is unresponding until display is ready.
Any way to speed this up?
You could turn on Preferences / Folders / Folder Display / Show generic icons for... all folders.
If things are fast then, then the problem could be a shell extension which something else has installed and which is slow to provide icons when asked. Or possibly antivirus blocking for a long time when the folders, shell extensions or other things they access are loaded by dopus.exe. But it will be difficult to work out the exact cause without admin rights, as the diagnostic tools all need that.