A small differentiation:
Story-wise this may be right. Character-strength-wise not. In my first playthrough in Elex One I did all sidequests, which were possible without faction, cleared all enemies from the map and would have been easiliy able to kill the end boss, but the game simply didn't allow me to enter that area. So I had to join a faction for the only reason to overcome this obstacle.
After that experience I was an advocate of the request, to allow factionless in Elex II and I like to believe that I am a small part of the reason, that PB made this now possible. And of course my first playthrough in Elex II was factionless...
By the way, even story-wise the independent group in the heroe's homebase would have been a sufficient neutral faction to justify factionless play even in Elex I.
Did I mention that I hated all the factions in Elex I?