A firewall, for instance, is a basic necessity. Even the crude android flavors. It includes the ability to lock out your "vendors" selectively and accurately.
My build is, hm, approaching it's fourth year, I think. No auto updates save for select apps. No complaints. No surprises. But I'm special, I don't do "phone for fun" and so have a fairly limited and hardened short list of requirements.
The most annoying thing on android is Google XXANY - by a wide, wide margin. I'll be itching to build a google-go-around on my next handset, for certain.
Save all those apps you like, for sure, I still depend on side-loading quite a few that have since gone by the wayside. At this juncture I have to take absolutely every bit of control that I can get my filthy paws wrapped around.