I am right there with you! I have been quilting for years and I still cannot get the 1/4 inch seam...no matter what I do, the block ends up too small. I've tried all the 'fixes' but no-go. Finally decided to forget it. I do my best and if things aren't perfect, nobody notices. I quilt for pleasure and for family/friends and they love all my quilts. I am never going to be a perfectionist but that's fine with me.
Having said that, I know there are those who want things 'right' and that's okay too. If you are like that, then keep trying. Having someone...... who knows how it's done.....to sit down with you will probably be the best solution.