It's definitely true that the better you drive, the less the assists kick in. But many expert drivers insist the assists hold them back, and I can see their point.
The following isn't even close to a scientifically-perfect comparison, but I think it illustrates the point. You could argue that things aren't close enough to make this a valid example, but it's the best I've got.
The left is one of the Q leaders, and the right is me. I tried to line up the frames so the positions on the track are as close as possible. And miracle of miracles, I happen to be taking this corner almost exactly the same as the leader:
View attachment 1240598
View attachment 1240599
The leader is in a 911 and I'm in the V12, so obviously that factors in. But even if it isn't perfect, it illustrates what most expert drivers say about how TCS can hold them back. Add that to how CA and ASM affect the ability to slide a little, and there's a definite difference.
Of course, in one respect, the point is moot. I'm pretty sure I could never come close to matching the near-perfection of the leader's driving, which means using these assists is like having a cheat code.
EDIT: Again, I realize this isn't a perfect comparison - probably not even close, if you think too much about it. But if nothing else, you gotta be a little impressed with both the fact that at this one corner, during this one lap, I'm driving so close to the Q leader. And that I did a pretty good job with the images.