Sure it does, in two different stages. First, when Team A is shooting, the skip of Team B is in the house and can sweep rocks out of the back of the house.
Second, the teams alternate in taking the shots, and one of the prime goals is to knock the opponents’ rocks out of play with your own shots. That counts as opposition to my mind.
I’d also concur with Hari Selden - sure, if you go to the local rink you’ll see some unathletic looking players - but is that any different from the local softball leagues? But when you get to the competitive levels, fitness counts - if you watched the recent World Cups, or the curling at the Olympics, you wouldn’t have seen any over-weight or out-of-shape players. These guys play long seasons and train hard.
Also, have any of the posters who are slamming curling ever actually curled? Trust me, three hours of running on the ice, keeping your balance, and sweeping the bejazus for a demanding skip is not a pristine activity - its sweaty, it keeps you puffing much like any other sport, and is very much an acquired skill where training is necessary. And that’s just the sweeping. Throwing the rocks requires aim, balance and a good appreciation of the ice.
And finally, so what’s wrong with a sport where you can chug a beer in play?