The pure consistency is one of the things that places this series above the rest. The analog style footage serves only to strengthen the intrigue of the series, and remains present throughout. Mystery is built gradually, so that the series still has a lot of unexplored depths while still showcasing a lot of interesting details.
All of the 3d environments look tangible and real, and on top of that a lot of the coloring in some shots especially looks great.
Also, there is some plot structure, enough for there to be a narrative to follow while still not giving away too many details. The result is a sort of freeform narrative, although it is much more structured than the typical layered analog horror franchise, EG Local 58 or The Mandela Catalogue.
A lot of the reasons this has become so popular have to do with how high quality it is. The analog aesthetic, the crisp sound design, the intuitive and consistent narrative, and the top notch editing (beginning sequence of Missing Persons, the entirety of Report) all combine to create this internally consistent and fascinating parallel world, that delivers while still leaving way for possibilities ahead.
As a result, I look forward to each next entry more than I look forward to most mainstream shows. Not superfluous, not lacking, just complex.