Apple does compete against and block other apps quite regularly. You can't change your default browser, heck you can't even install a different web rendering engine from the one they provide (which is another way of forcing app distribution to go through the web store since other browser vendors can't push the web forward on iOS).

The crux of the Epic case is that there's no alternative to the app store. If there were an alternative to the app store, Epic would not be subject to Apple's capricious whims or 30% tax. So, yes, Apple is blocking competition with their services on their platform.