I was (and still stand by it, as it is a personal preference) hoping to see more of a "classic" faction system with "classic" joinable factions and faction unique content, but it is clear that the narrative frame that was picked in the end - and you have to pick one - doesn't support this model of joinable faction in the classic sense.
But at the same time I'm yet not overly disappointed. How so? A simple game is my shining positive example:
Fallout New Vegas
It's roughly the same narrative frame. You have your more or less set protagonist and 'role', you have a main plot, side quests, a world, big notable factions, etc. You cannot join either of the big factions at all - only help or hinder, and join some smaller or secondary factions.
Despite never being able to formally join a notable faction without any third party modifications, it offered an immersive and close experience to me where closely working with factions, in favor, felt like being part of the faction due to how it was handled and how you were greeted depending on a rudimentary reputation system. This personal preference or even "nitpick" I had was swept away, I got lost in the immersive world and enjoyed it without having any issues.
I'm guessing or hoping that Cyberpunk 2077 will be similar, with a lack of a classic reputation system based on + or - rep values.