Nope, an aftermarket lens works well because Bill Fox is an excellent shooter and is familiar with his gear and actually uses it rather than sitting around making excuses and pining for a new gizmoflex wonderglass 1000 that will solve all his problems. Tamron and the rest will do a very good job for most of us if we learn to use them. Even if it would be 'better' with the prime L series or ED lens. Learn to use what you have to the maximum and you maximize your possibilities. You also get better and better as a photographer so when you do get the new glass you will be in a good position to actually use it.
Talent plays a big part in getting good results.
New lenses are no answer if you don't know what you are doing. I will say it again, mediocre photographers make mediocre pictures-big expensive lenses just make more expensive mediocre pictures for these jokers. But, if you actually need the lens, get the best one you can afford. After all, the lens takes the photo. If you normally work with autofocus, get the autofocus lenses designed to work with your system whether prime or aftermarket.