When it comes to email front-ends, you certainly have a plethora of choices, so no way one app is trying to force you down one and only one road.
I am an Office 365 user and although I use the Mail app from time to time, when it comes to significant email activities, I use the browser front-end, not the Mail app. As a matter of fact, prior to joining Office 365, I used to be an extensive Outlook app user but I have not looked back since switching to Office 365.