None of my quilts will ever be prize winners because my quilts are made with love and mistakes. If it really bugs me I'll fix it, if not, then life is too short to worry about a wavy seam or crooked intersection, in my humble opinion - chances are after the quilt has been washed a few times and drug around on the floor, that wavy seam or intersection will be the last thing anyone ever thinks about.
For me precuts and kits are a matter of convenience and availability...not whether I'm fussy or not. I'll take my chances on the sizes sometimes and roll with the punches -- gives me creative license for changes as needed. Guess I'm a more laid back type of quilter that does it for fun and not for aggravation.