I suppose that's dependant on who you learn from. My Tae Kwon Do days were much like you say, not actually making much contact and using very little power when you did; which I think was of benefit to me as a child, however the guys who coached me in Karate were much more realistic, one was a former Thai Boxer and both were BJJ purple belts at a time when people training BJJ were very few and far between (we used to travel 3 hours to the black belt) We also had a few military guys at the club that liked to push it; I was probably quite lucky in where I trained.
I'm also lucky now, as the guy heading up the Wing Chun club is open to different ideas and styles and doesn't hold the commonly held (in trad MA circles) backward idea that their one style is able to beat all others
He's actually asked about holds, chokes etc. that can be incorporated into the system, so in my mind that's a good mentality! Trust me, I've walked into many gyms/dojos etc over the years and walked rapidly back out on witnessing the crap being taught and the backward mentality of the instructors.
Nobody punches better than a boxer, that's pretty irrefutable.
I agree with your point about some people being able to win fights without throwing a single kick, I've been witness to it many times; then again I've seen fights won purely from powerful well placed kicks without a single punch been thrown.
All martial Arts have limitations, as I said its all relative to what you are doing with what, an MMA fighter in a boxing match isn't well placed, nobody would do much against a 50cal.
However Wing Chun isn't a competitive martial art and I don't approach it as such, in fact that's what appealed to me, for the time being I don't have that competitive MA mind set anymore.
I'm confident that with my existing knowledge base I can take some positives from Wing Chun to add to my abilities and enjoy the process at the same time.
GSP was/is? awesome and he's always been right at the top of my favourite pound for pound fighters, completely well rounded and kept away from most of the trash talking.