Yes it is.

iOS controls a sufficient part of US revenue that wider ecosystem effects on what is permitted speech come directly from the app store terms, or at least in some cases about trying to second guess the inconsistently applied, arbitrary and vague as hell App Store rules.

We've got direct testimony from all sorts of app makers that what speech they do and do not censor on the platform (especially around sex, impacting the fundamental liberties and safety of sex workers, queer communities, artists and educators) is directly because their business is such that they need to watch the terms of the app store.

We've seen examples in China of Apple blocking apps that literally lead to people failing to escape authoritarian governments and them disappearing, quite possibly to their death.

Liberty is the fundamental reason that a singular control of what software can be run on mobile device is a thing too dangerous to be allowed to exist. Competition law is probably the most expedient route to fix it, but a centralised app store should be a criminal act on it's own merits.