Large corporations with large marketshare can easily do significantly uncompetitive things, with little effort on their part.

No monopoly required.

All that is required is that they have large marketshare, an important product, and it is difficult for users to change to alternatives, or avoid its uncompetitive behavior.

Choosing a phone involves balancing numerous features of devices. There is no phone market with the thousands of competing devices it would take to really cover what a customer might ideally want. So choices often balance so many things, involve so much practical investment, that they make switching devices over a few things, or even many things, from awfully unpleasant to very difficult.

And, with great market power, comes great responsibility: to not become a barrier to competitive innovation and hard work.

By definition, Apple's strict gatekeeping App Store, a significant feature on a significant general purpose computing platform, is anti-competitive. There is no technical reason why side loading or side-stores couldn't thrive, on such a general purpose device intertwined in all our lives.

Onerous fees and terms and selective limitation (relative to Apple's own offerings) for developers make it even more anticompetitive.

Of course, anyone who likes having fewer options, or just the options they have now, is free to not explore others. For now and forever. Amen.