I've read through this whole thread and its amazing that there are such diverse reactions.
I agree that most classes should be open ESC with the limiting factor being the motor size for the Novice, Stock, Sportsman (all the same) Class. If the 17.5 is too fast for this class go to 21.5 and optimize your choice of chassis, motor, ESC, tires and body. Most people don't know how to set a rear wing on any class body from TC, to WGT. Learn to be fast driving, not bench racing your parts. Put in 3 or 4 hours a week on practice and setup. Use tools and build your knowledge and skills on your cars, not your wallet. After you have enough understanding or can kick everyone's butt, then move up to Open, Mod, Masters (still the same class) and learn some more.
Every kid who sees an RC car for the first time, from 2 to 92, will ask "How fast does that one go?" Just try and tell that kid that even if he spends $1000 on a full on race setup and enough spare parts to rebuild his car 10 times that his car is fast, but he will have to learn how to drive it. You get dirty looks, the posing and posturing, and even "but I play video games!". I can say with all honesty, that I almost fell into this trap when I came back to the hobby. I picked up lower wind motors, but geared down to slow the cars(almost common sense). My son wanted 13.5s found out Trans Am with 21.5 was a bit fast for him.
All that being said. The only true Spec classes are RCGT, TA and F1 where scale realism is more important than shear speed. locked ESCs and high wind motors belong here. Besides an F1 with a 21.5 and no timing ESC is about as fast, fun and cheap to race as anything you can put your hands on.