It could but so could being out of adjustment or an improperly installed clutch cable.
I think typically it's just the clutch plates that seize together but if it sat long enough the whole clutch cage could be stuck.
My clutch plates were stuck after the bike sat for 10 years but the clutch still had full range of motion. Sounds like yours sat for at least ten more than that.
Does it die when you shift gears or when you release the clutch lever?
There is a technique to try to break the clutch free without taking anything apart but I think you might be past the point of it being effective. It involves securing the front wheel against a solid wall to prevent the bike from moving, revving into higher RPMs, shifting into a higher gear, and then suddenly releasing the clutch.
There is a better description on here somewhere and other member who posted about stuck clutches.
I'd try the clutch adjustment first. You must have had the left side drive sprocket cover off to install the new clutch cable so I'd assume the push mechanism there is good but they can seize up from prolonged neglect.
If everything is good from the clutch lever down to the left side of the motor you'll have to look at the clutch cage on the right side.
The clutch plates can be seen through the dip stick hole. Might be able to get some idea of their condition from looking at them there. Visible rust build-up bridging the plates is probably the worst-case. I tried to wiggle my plates free with a screwdriver through the hole but it didn't help any. In hindsight it's probably not the best idea in case it damages the clutch plates.
If the plates are stuck and the clutch bumping method doesn't work you're most likely looking at taking the clutch out, cleaning or replacing some parts, oiling them, and reinstalling.