Office apps are very slow to start on Mac

nic222  Just to rule out a bunch of things and some random things to try... Generally this type of issue is difficult to troubleshoot as it can be so many things. From personal experience, I am currently running Office on a M1 MacBook, completely up to date macOS, and there's zero slowdown right now. If all else fails, see if you can reach out to Microsoft Support. 

1) Any chance you can update to the latest version of macOS Big Sur (11.5.2). There's been numerous bug fixes, including fixes of known performance issues.

2) Do you know if there's any add-ins installed and/or pushed via central deployment in Microsoft 365? Such add-ins may cause slowdowns as well. For example, recently I've experienced slowdowns due to the installation of a third party templating add-in.

3) Does your system have antivirus software installed? If so, any chance you could temporarily disable it just to start one of the affected Office apps to see if this improves things? Please note the temporarily part, and while it's disabled, only try running Office apps and re-enable it as soon as possible.

4) Specifically for Outlook, sometimes it becomes slow to the huge amount of email to be downloaded, do you happen to have a very large mailbox?

5) To rule out any sign in/activation issues, are you sure you can connect to the Internet just fine? Your system is not using a proxy of some sort which may be blocking connectivity or causing slowdowns?