The COT cars may be identical, the tires may be the same, however, the team with better funding and more talented drivers and crew succeed.
How exactly could the series be fair if the teams were allowed to "run what they brung?" You'd see cars with over-sized engines, tricked out fuel systems, traction control, etc.
I've been a NASCAR fan since I was a kid, so conservatively, over 50 years. In my opinion, we're seeing better racing today than we ever have. Safety issues have been addressed, and we're not seeing drivers die on a regular basis as we did back in the past.