What you described in your "rant" is that perfect vision that everyone has about the roleplay they want to see and experience, but in reality it sadly is a far fetched idea that most likely will never happen, but at the same time not impossible.
I could see this happening, but not with a great leader on top of it and in order to be a great leader you probably have to be either part of a big community already or be a content creator that has a big community, because those people have already banded together and have their "leader".
The other thing to understand is why do we have small towns and villages every 10km apart. The main reason is because most of the people join with their friends and create their little communities, because they want to represent their own group. If you and your 5 buddies become a part of the massive 100-200 people community then you just a number, but everyone wants to be the hero of their own story. I want to be the inn keeper that everyone knows, I want to be the best blacksmith in the town, I want to be that fierce warrior that everyone talks about, I want to be part of the council etc.
While it is possible, I believe the small villages all across the map is not a bad thing either, because that allows you to have the RP opportunities while on the travels, gives you then the stories to tell around some ale in the inn in the big city.
Overall, same as you, I think such thing would be impressive and I would love to see that, but me personally, I would still want to try my own little corner community before joining, as an outsider, such big community and trying to find my place in all of it.