Completely agree. We went on this ride after I told my DH how thrilling it is and that he would have a good time. I hadn't been on it since they re-did it because I never wanted to wait in line.
We used our fast passes, and had to do the whole design thing, and it just felt like a waste of time. We couldn't care less how "our design" ranked against the metrics of all the tests.
My husband liked the actual ride part, but bc of the whole process, he never wants to go on it again.
I told him, if we do, we have to do single rider, since it's not so extensive in creating a useless car.
That being said, DH and I are in our 30s with no kids... If you think your kids would really enjoy spending 5 or so minutes designing a car that really has nothing to do with the ride, then maybe it's worth going thru the line.