It depends on the sport.
If you're goose hunting, an 18" cylinder bore probably isn't going to do the job very well.
Things to keep in mind: Years ago the NRA Dope Bag did a test with a Marlin Goose Gun with the 36" barrel. They attached a choke device on the barrel then patterned and chronograph it. They then cut the barrel down in 1 inch increments and tested again.
Their results said that anything that was going to happen ballistically in a shotgun barrel was going to happen within 18".
Anything over 28" and you started to LOSE due to friction.
Things didn't really go to hell until the length was under 12".
Length has little, or nothing to do with tight patterns. An 18" full choke barrel will shoot tighter patterns than a 28" modified choke barrel.
The idea that longer barrels shoot "harder" or "farther" is a left-over from black powder days when longer barrels burned the powder better than short barrels.
The biggest determiner of capability is the choke. If you have a screw-in choke, or can have one installed in your barrel, you can use an 18" barreled gun for a wide range of sports.
Although the longer barrels swing and point better than the short barrels and you may not excel, you can use a short barrel.
Back in the 50's the Winchester factory rep used to use a short Model 12 as a quail gun. He could have any Winchester gun he wanted, setup any way he wanted, including the expensive Winchester 21 double. His choice was the Model 12 with an 18" cylinder bore barrel.
People ragged him about his "riot gun"....until they saw him shoot.
While everyone else had to wait until the birds were far enough away not to be blown to bits, he was fast off the mark, shooting as soon as the bird was up, and at very short range.
He was deadly and always got his limit.
So, if you have an 18" cylinder bore, pick your sport, and give it a try, you have nothing to lose. The secret is knowing your gun. Take it to the range and pattern it with various shot at different ranges. This will indicate what it will do, and what it won't be suitable for.
Patterning will probably tell you that the cylinder bore isn't too good for turkey hunting, goose hunting, or trap.
It will be good for quail, deer, possibly skeet, and.........?????