You can either pick a battle that you cannot win (assuming you're not the one in charge of the many millions such a migration would cost). You can just deal with it, or you can look for better circumstances.

You say you're convincing people, management sees a trouble maker who's spreading unhappiness.

In my opinion, it's better to save your energy for something where it can make a change, not a futile attempt at trying to make an institute drop Outlook or Teams, or whatever shitty software we're talking about.

But hey, this is just my advice. You do you.