Are you using it on Apple Silicon? If so, then Rosetta is the reason why Excel are not performant on macOS. Office365 for macOS are using x86 code at the moment, Office team is rewriting Excel to work on Apple Silicon/ARM. They have a preview build out, I'm not sure when they will release the stable version. I recalled they said it should be release in Spring or Summer.

If you have Excel running, open the Activity Monitor and find the app in the list. Then look at "Kind" column, you will see "Intel" listed. So that's why Office365 are sluggish on it.