Thank you once again for contradicting yourself with your own words. Just like anyone can sign in here, any developer can also join App Store. Mac Rumors doesn’t prevent you from posting comments but it does serve the right to remove your comment or in extreme cases remove your account if you don’t stick to their guidelines. Same applies to App Store rules.Yeah, what's cute. But, no, this will not stand in Economics or in court.
Just based on the fact that there are no barriers to entry, disregarding all else, this would be called "perfectly competitive", not "monopolistic".
Just like Mac Rumors does not prevent you from posting comments in other sites, Apple also does not prevent developers from developing and distributing their apps on other platforms.
By your own definition, App Store - as well as Mac Rumors - is “perfectly competitive”.