Exactly. I have NEVER used one of those set up sheets. I build kits according to kit set up and change things that I know work for me at my track and then I adjust from there.
Download the Cheat sheets app from AE it tells you what changes to make. Go online, competition X has a great set up tips page. Instead of trying set up after set up sit down and read about how to set your car up.
Learn what Roll Center is and how to adjust it, understand what shock oils and sway bars do and what they will do to your car. When you go out on the track LISTEN to you car. Into the corner, mid corner out of the corner, on the brakes, on the gas, coasting, landing, take off, every single thing you command your car to do is an input, if the car is not set up to receive those inputs it will tell you. You then make changes that the car needs to accept those inputs.
Perfect example, just yesterday I went for a season opener 1/8th scale race with a Mugen MBX7R Eco that I bought used. I didnt change anything on the car, just put my electronics in it and threw it on track. Car was very loose in the back. no forward grip and needed more side bite. First practice I added rear toe and some anti squat, got better but I wanted more so I move the hubs forward. Car was great Qualified in the D main, bumped to the C and was challenging for a bump to the B at one point but got t angled up in lapped traffic and ended up 4th.