yes let's rule out incredibly intuitive controls relative to the rest of the genre at the time, and gameplay systems like auto regen, both of which lent themselves well to infantry combat as well as land and air vehicular combat alike. Handwave away the significance and novelty of Halo's extensive multiplayer functionality (which back then wasn't as dime a dozen, certainly not as fleshed out anywhere on consoles), the forward thinking and well designed campaign sandbox featuring AI that was balls out incredible for the time, brilliant multiplayer balancing alongside (mostly) quality maps - featuring a handful of nifty non-hitscan weapon concepts alongside shooter staples - that came together for a gameplay loop that felt distinctly fresh and different, etc. and certainly do not consider the documented impact Halo had on the genre in the console space as a result of all these things
There's reasons why Halo was one of the first FPSes on consoles to 'play great.' That in and of itself is revolutionary, and it's for all the reasons I just detailed, as far as I can discern via my understanding of the term 'revolutionary'. Would you hesitate to call Super Mario Brothers a revolutionary platformer because there were competent enough platformers made beforehand? Would that they exist in a similar fashion on paper ("point and shoot like doom", jump and run leik pitfall) diminish SMB's scrolling levels, subtle gameplay hints and cues, perfect control over the character, etc. and the impact that SMB had on the appeal, marketability and playability of the genre moving forward?