This is further crippled by how the increasingly tight security measures in Android make harder and harder to add functionality that is considered "system-level" and is as deeply integrated as the Play Store.
You can't simply install F-droid and expect the same level of user friendliness and automatic app updates as in the official Play Store. Without esoteric, hackish and warranty-voiding rooting methods, you need to give manual user confirmation for every small update. You need to update 30 apps that accumulated because you forgot to manually update each of them? get prepared for going 30 times thought the same process of pressing buttons and giving confirmation for each of them.