The performance of the new desktop Yahoo Mail is still extremely poor. I never experienced anything like this before the new windows desktop was rolled out. Quite frequently when deleting/moving emails or navigating between different folders, my session hangs (waiting 10-15 secons or longer for things to update and display the desired content), leading me to not want to wait and simply refreshing my (typically) EDGE browser session. Note this happens on the latest/updated versions of: EDGE, FireFox, Chrome, Duck Duck Go and Norton's Private Browsers on my HP laptop running the latest Windows 11 OS (all updates applied). I don't want to go back to the old Yahoo Mail, but hopefully you're addressing this issue.

Note: Yahoo Mobile app email runs fine without any issues whatsoever on my iPhone