I like to compare arena shooters vs. Fortnite/Overwatch as chess vs. Settlers of Catan. Arena shooters were much more "open play" in the sense that there were few enough game mechanics that you could mostly guess your opponents' tactics and it often came down to execution and minute variations in the gameplay.
The newer shooters add many, many game mechanics that complicate and randomize the game. Overwatch's large stable of characters, for example. This creates a problem where part of your skill is reading matchups from an intractably large number of factors, then executing on it.
I don't consider either to be superior, but the games put emphasis on and reward different skills.
For newcomers this resulted in dying horrible most of the time, all the time.
Not even close to the extent you need to have it for a fast-paced AFPS. Watch some top-level quake gameplay and compare it to top-level Overwatch gameplay, it's night and day. Hell, some OW characters even aim for you or don't need to aim at all to be effective (Winston for example)
>but now there are a host of other mechanical, tactical and cooperative skills to master on top of that
Cooperation sure, OW does put more of an emphasis on teamwork. But as far as mechanical and tactical skill goes I don't see how you can make that argument unless you've never played an AFPS
But the scene isn't as big for those as it is for 1v1, because its already overwhelming trying to track two people operating at peak performance, let alone 8 or 12. Its a niche of a niche.