I don't disagree with you, but the other thing to think of what mods would be necessary to make the Su-27 and -30 durable enough to endure the rigors of cat launches? Are those mods feasible? Even a "full-size" carrier doesn't compare to a runway.
I'm not sure what goes into a catapult launch modifcation. The SU-27K is the carrier version of the SU-27. It has been modified with arresting hook, reinforced landing gear, etc. Not sure what else would need to be done.