It's weird that any competitive chess player would say the opening phase doesn't matter. (How you play it!)
Indeed. It's often a misconception that booked up players don't know how to play endgame inasmuch as saying tactical players don't know how to play positional. But to outright say that one plays a chess game simply on a move to move basis, regardless of the "phase" of the game seems pretentious.
If one were universal, okay I concede to the player whose stats include depth of opening repertoire, middlegame prowess, and solid endgame theory. But, heh, unless you're on another level than the rest of here posting~I would say you're full of it.
Opening novelties: who comes up with this stuff? It's not pure engine work I guess. It's creativity of the human mind, the thing that makes Chess beautiful. What makes Chess beautiful is our limited human mind. Limited calculating ability, limited memory, limited concentration, and others. Come to think of it If we can calculate and store information like computer engines and table databases then Chess will become boring! That will be the beginning of the end of the game.