I'd say the Android app store is a nice balance.
Also, if you want to install some other, less-well maintained app store on your Android, that's also possible (on non-rooted phones, too). Indeed, I've got F-Droid enabled on my Android.
That said, if Google ever pulls the ability to sideload apps on non-rooted phones, I'll not be happy at all.
When Fortnite was distributed outside the Play store I thought that would be the catalyst for removing side-loading permissions, only retaining them over ADB so developers would not be totally screwed. Maybe the news of that arrived too late in the Q cycle for it to be implemented. I'm sure that one day on-the-fly side-loading is going away. Maybe not in Android Q, but in R or S definitely. It's too consumer-friendly and useful! Removing it will "help user's security" while at the same time removing the ability to install 3rd party VPN-faking ad-removers or games like Fortnite that don't have to pay Google 30%.
There's no three day wait to install an APK, either.
There's a three day wait to get your app in Google's store, which isn't the only possible distribution method for Android apps.
So far this has not caused any signifficant issues - rather gave enough time for testing & caught a lot of breakage before it broke someones Fedora installation.