I am not sure what you are trying to say here. I have never had an Android system that did not have OTA updates. Everything included... I usually like to install the apps I want?
As for microG, I think it's debatable. Is it better to have microG contacting the Google servers or sandboxed Play Services going through a Graphene-powered proxy? And say you have microG going through a Murena proxy (do they do that?), is that significantly better than sandboxed Play Services? At the end of the day, your system is made mostly of code written by Google (AOSP).
> The Murena e/OS offering in particular is simple enough that the non-nerds
Yes, I think it's what makes Murena successful. It's surprisingly simple to install GrapheneOS on a Pixel (you follow a wizard on a Chromium browser and click "next" a bunch of times), but many people are scare just by the idea.