My dad is 46 & he gets shit on in every multiplayer mode. One of my professors is about 40, and he's terrible. Most of my friends are about 16-25, for the most part; they're all good. I don't have any little kids added, but I have played with them. I've played with some amazing little dudes, but I'll say 90% of anyone under 13 sucks.
It's not just reaction time. It's more about how well you move around the map, how you strategize, how quickly you can aim on a target from range, and a bunch of other things. If your only strong point is reaction time, then that won't make up for other required skills.