If I've got a block wrong, that will be fixed. If sometimes points or seams aren't perfect, that often is left.
But each quilt is different, and one I'm working on now, it has kalidescope blocks, and I wanted them to be near perfect - so some got sewn 2- 3 times!
I learned doing home construction - there is never an easier time to fix a mistake than when you first notice it. I try not to think of it as "wasted time" but just part of the process.