I have the same thoughts as the OP at times. I watch the fast guys go through a corner and it looks like they are able to run much faster than I am. So I ask myself, am I running the same line? If not, can I? If I can't run that line, why not? What is preventing me from running that line - not enough steering, too much steering, problems out of the previous corner, etc... Then I try to adjust to get the balance to allow me to run the line. Once I get to where I feel I can run the line that everyone else is running and the car feels good, then I look to see where my times are compared to the fast guys. If I am running the line, and the car balance is good, then it may be the car just can't generate the grip with the current setup. Adjust some more. If all of your adjustments make things worse, then you have reached the limit of either the car or your setup knowledge.
I keep this link on my phone all the time:
R/C Car Handling - Touring Car Setup Guide
It is a bit older, but I think the info is pretty sound. It matches up with other stuff I have read.
But at the end of the day, as everyone has said, a good driver with a mediocre car will beat a mediocre driver with a great car 9 times out of 10.
IndyRC_Racer has helped me a ton. He has taken my crappy setup car and immediately improved on my times by a half second. Then he has offered suggestions and I have worked on my car. I have learned a bunch from him and I use that to work on my setups. I still don't think my car is perfect, but it is getting closer to what I want. And he will still go out an beat me by a half second with it!
