So, it occurred to me that in my comments on sports here I missed one very large elephant in the room that makes competitive sports… difficult.
Namely, the number of species, and then the number of clades of those species, and that’s before we start getting into individual-level modifications, which leads to truly astonishing levels of ability divergence in various areas, many of them qualifying as “special abilities”.
To some degree, as we do, you can try and level that with rules, but that’s limited in the first place unless you go for a blanket “only baselines, or at least only alphas, of one single species, can play” – which very much limits the number of players and amount of interest you’ll get – you’re dealing with an entire culture of people whose natural inclination is to exploit the hell out of loopholes in anything that seems “unfairly restrictive”.
And it’s not as if this “ain’t no rule” attitude wasn’t giving referees plenty of headaches long before there were any other species around. “Yes, the rulebook says that the ball must be in a player’s possession when it enters the scoring zone, but there Ain’t No Rule that says another player can’t PK-throw the possessing player into said zone, right?”
(Minor plot point from the Contact Novel That Shall Never Be Written: the first football team to come up with the notion of hiring a kaeth fullback. After the ensuing (mostly metaphorical) carnage, it didn’t take the NFL long to come up with the “must weigh under 400 lbs.” rule.)
As such, those attempts at competitive sports leagues which do exist tend to have rulebooks the approximate size of the unabridged Encylopaedia Britannica, and add about a chapter to their length every game as people find new, obscure abilities or new, not-yet-forbidden synergies of abilities to exploit.
Or they go the free-for-all route, but that’s less “competitive sport” and more “exhibition grand meleé, specializing in deviousness”.