Another axis is "game sense" which is a combination of map, player and meta knowledge. What are the most common routes taken by the enemy on this map? If we secure this site, what are the most likely avenues of approach the enemy will take? What weapons are my opponents most likely to buy based on the current phase of the match, and how can we respond? A player with better game sense can be competitive with people who are better at those twitch reactions by setting up scenarios which favor tactical advantage over raw shooting skill. Communication is key here as well. You have to be able to get your team onboard with setting up these scenarios. These skill do not decrease with age except at the extreme end.
Obviously the best players are great at both of these. That's why many pro players have videos out there of them destroying people who are cheating with an aim bot. Their knowledge of the game and maps give them such an advantage they can overcome literally impossible reaction times from opponents. But being competent at either one will enable to you enjoy and be competitive in these games, especially if they use rank based match making to ensure you're not getting matched against those super players. At the lower to mid rank of these games, you can see examples all over the place where individuals are competent at one of these dimensions, but there is almost always a glaring gap in the other. Whether it's the person who can consistently get head shots but also runs themselves into unfavorable positions so they keep dying, to the people who are trying to coordinate and plan but lose almost every one on one engagement. As you get older you've got to rely more on that game sense than you can rely on your raw reactions and that puts a real upper age limit on pro level competition, but shouldn't in any way prevent people from being able to compete in the pleb arenas.