No, they don't. Most antitrust cases don't involve monopolies, since those are actually quite rare, and most monopolies don't involve anticompetitive behavior.

Antitrust is about regulating anticompetitive market activities, which ranges from price fixing to monopolies.

I'm sure that will be consolation to the growing number of victims whose businesses and livelihoods were destroyed when an overworked reviewer or an algorithm allowed to go rampant kicked out their products from the app stores where the overwhelming majority of users could discover them.

Your definition of monopolies and applicable antitrust rules is divorced from reality, and from the legal framework based on which these monopolies have been repeatedly fined, and will be forced to open up their platforms.