1. You can't run all the rules on your inbox to sweep the piled up email after a weekend reboot. No such option while it is still present in the legacy native Outlook.
2. You have no option of deleting an entry in your calendar without sending a decline. I am in many groups and sometimes just want to clean up my calendar without sending declines. Again, very much present in the native program.
No one expects genuine innovation from MS, but at least they could put some effort into feature parity. Too much to ask for in the days of Copilot I guess.