Apple's closed-wall approach to app availability is a positive feature to most people but it is anticompetitive. Users should have the option of buying and installing apps from other sources. It should be their choice to assume the risk.
Posters are scratching their heads over the price argument because they are limiting themselves to the free or dollar apps. They are ignoring the costlier subscription apps that have to factor in Apple's generous take. Over time, Apple's markup can add up to $$$ for the consumer. Do these posters think the $Bn app store revenues came from free apps?
You do know that iOS updates are free cause Apple is getting that "take" to fund iOS development (and my guess MacOS as well)? Part of the reason why Google doesn't like people not using the Play Store or Google Search (in particular in China) cause they lose out ads revenue which is what Google make their money from.
And users do have the option of buying and installing apps from other sources, just jailbreak their phones and this is legal!
And you mentioned antivirus? Seriously? Why don't you just switch to Android, they're doing great there.