> any added features or customizations

That's not only about UI. Most people want customizations / features that enable things like 4G radio, wifi and graphics. What would be the point otherwise?

Maybe I should have been a bit more specific, but I was mostly just talking about UI features and customizations. I have no problems with a ROM modifying stock Android under the hood if it's necessary to enable basic hardware functionality. The point is to keep modifications to a bare minimum, to limit the overhead required to support each new Android release, and to maximize the number of devices the ROM is able to support given limited resources.

I was going to point you to the Pure series of roms by Beanstown, but I don't understand your question... You don't want ANY custom stuff at all or features, then what's the point? Just install stock android...?

"Stock Android" is only stock Android on Google-branded devices.

I don't understand this sentence. Google only has a single phone that has only been out for like 1 day now, the Pixel. And it's not even stock Android, it's got extra features that the stock Nougat doesn't have. Again though, I think this whole thing is moot, because lots of phones have roms on xda that is basically just stock android with no customizations, so just install that and be done with it.

I said Google-branded, not Google-manufactured. The Nexus line is what people typically understand by "stock Android".

The point isn't that there are no vanilla AOSP ROMs for most devices. The point is that they usually suck, and a reputable well-supported one that actually worked properly would be a massive innovation.

ADP1, Nexus One, Galaxy Nexus, Nexus 4, Nexus 5, Nexus 6P.

When people say "Google's phones" it is generally understood to mean the unlocked line of Nexus devices that they sell directly and provide updates/firmware images for directly.