Stock rom without root was pretty decent for me. No ads at all. However, I only use free software apps mostly from F-Droid (and uBlock Origin takes care of the web). I knew that this was putting myself in a bubble, but I had not realized that the experience of using a phone for a lot of people must be that annoying. What a shame. Computers should serve humans, not the other way round!

I discovered Google Play's App Store on someone else's phone, that was painful and stressful. But what you are describing seems hellish.

I used to root the devices I got. Relying on CM supporting my device or totally breaking carrier updates got old though. I switched to Google Fi and am using a Nexus 6P (Android 8) and it's really nice.

I wanted to get a PCAP from an app a few nights ago, I was surprised it was possible without root. Now there are apps that can act as a VPN to sniff traffic. Having the most up to date firmware and Google Fi's international rates are worth giving up root to me.

It would be nice if they built in secure root access interface to Android though.

The main problem with rooting my phone is that a number of apps I use will stop working, including the de facto standard mobile payment app in my country.

If you rein in the notifications (ie. switch them all off), use Firefox with uBlock Origin (or Firefox Focus) and avoid using apps with obnoxious ads (or switch to the paid versions), Android as of 2017 is quite nice.