The main one for me is the complete lack of control of network traffic. Other than a VPN loopback app, which is pretty janky, there is no way to disable network traffic per app. Even with a VPN loopback, there is no way to only allow network traffic when then app is in the foreground. There is no way to set network traffic to block by default and ask the user for permission when network access is needed. These restrictions are ABSOLUTELY DEADLY for user privacy and I don't understand why everyone isn't screaming at the top of their lungs from rooftops about these problems.
It's quite obvious with a 2 seconds of thought that these deficiencies were intentional to maintain Google's advertising monopoly, but I don't want a crippled OS to support Google's abhorrent business model.
It's absolutely mind boggling. It almost makes me want to join the LineageOS project to close these loopholes.