Slightly disagree. In TX, we ran very well attended carbines in an IDPA format and the usual gun was an AR pattern. There were some Ruger PCC or 9 mm ARs. Had a guy who ran a Garand and one guy with a bolt gun quite well. The lever action guy was a flop. Some 22 LR AR pattern. Using 223s in a setups for carbines is better than a USPSA pistol set up with 9mm carbines. I do think they are fun to run. I've mentioned a guy who shot a fancy 9mm AR type with a dot and a green laser at our carry gun match - sight, that was a bit much.
Today my bad knee is murderous. So at the match, I will stroll between shooting positions. Don't need to pitch over. Whining, I am but that's what I do. Some of us older toots look more to the A count as total time ain't for us. Of course, you don't want to shoot it in bullseye mode.