Action adventure is a qualifier on the story, not the game. It is undoubtedly an action-adventure story. In my opinion, it is also an aRPG (action Role Playing Game - much like TW3 was and aRPG).
Before I go further, I want to say that I really do feel like we try too hard to fit games into genre boxes. RPG isn't super helpful as a descriptor other than from a 10,000 foot marketing level for players, because no one can seem to agree on the specifics about what makes an RPG and RPG. Most of the time we can get it down to some combination of choices and consequences and stats impacting gameplay ... but more specific than that and it all falls apart.
1. Choices and Consequences - Cyberpunk 2077 has a non-linear branching narrative that is impacted by character choices for both some individual quests as well as the main questline. Built into that is a very good branching dialogue system that is frequently heavily flavored by background or stats. All those choices fit within the range of outcomes CDPR thought was appropriate for the stories they wanted to tell, but it's undeniable there are choices there that have consequences to the story. This is the most important aspect of any RPG IMO.
2. Character Creation / Progression / Mechanics - It has a character creation and progression system that allows for the character to become more proficient at overcoming challenges throughout the story using a variety of play styles in navigating the world and level design. Once again, those progression systems all fit within a range that CDPR wanted to tell it's story, but they are undeniably there.
Now it's not a "be whatever you want to be, do whatever you want to do" RPG, but CDPR has said for a long time that
story comes first in this game. That means the possibilities for the player character have to fit within that narrative they want to tell, just like TW3. CDPR's whole thing since they started making games is trying to blend (a) great stories with (b) fun gameplay using (c) RPG mechanics. That requires some compromises for each of those three things.
Now the RPG systems may not be there to the degree that some players would prefer, but they are there. You can of course argue it's the the illusion of choice instead of "real" choice, or the illusion of progression rather than "real" progression, but those are arguments about the amount of those features rather than if they are there at all. That fact that they are there, and reasonably robust (IMO), means that it's definitely an RPG for me.
TLDR; In my opinion it's definitely an RPG and an action-adventure story. Those aren't mutually exclusive.