Your security would not be compromised. I take it you are above the average compared to most unassuming users, so you would know trustworthy app stores to install apps from.
The beauty of iOS is in its walled garden. Even the less-than-average user doesn't have to be mindful of where they get their apps from. Apple as a gatekeeper upholds at least some standard for the apps. "App store X" might have entirely different standards for usability, stability & security – or no standards at all.
A jungle, as I said in my previous comment, to the very potential detriment of user-experience, quality and security.
AppStore, 30% cut, over a billion users. Where's the problem? Breaking it and paving way for unforeseen problems is stupid for everyone, devs and users alike.
Still today "power users" can jailbreak their phones and go on an expedition into the jungle. So I wonder if Apple introducing a less restricted (less walled) Power User Mode would alleviate some of the controversy? Power User Mode would of course come with a disclaimer that after enabling it, you are no longer eligible for Apple Support. Why should Apple support something they have not vetted, approved and distributed?
Which, again, brings me to the jungle – from the user's point of view. Wanna do what you want? Choose Android. As we all know, it's already what a lot of people love
iOS is an alternative choice. It's good to have choice. Ironically, many people here wanting more choice are advocating for removing the choice that iOS offers.