OK. You've convinced me. Competitive shooting only improves trigger control, indexing, accuracy, safe weapon handling, target acquisition, transitions, recoil control, shooting on the move, shooting moving targets, shooting in different positions, drawing from a holster, shooting one handed, shooting targets of varying size, difficulty, and distance, and doing those things under the pressure of the clock. Clearly those are skills that are of little importance in self defense or tactical shooting.
Oddly enough, I've taken two self defense/tactical pistol classes, and you know what skills they taught? The same skills I put to use in every match I shoot (see the list above for a sample). At the Chapman School, we did spend 10-15% of our time shooting from behind barricades, but then we shoot around barricades in competition, too.
FWIW, I've never seen anyone argue that USPSA/IPSC/IDPA/Steel Challenge/NRA Action Pistol/Bullseye/whatever discipline you prefer is a total and complete SD training solution. By the same token, the SD/Tactical instructors I've worked with made it clear that they didn't consider their training to be a 100% training solution. They seemed to think that regular practice and even <gasp> competitive shooting would be useful ways to maintain and improve our skills.