My daughter recently wanted me to repair a quilt that was extremely worn, the top fabric has just worn away in many of the blocks. No way to take quilt apart. Luckily it was a simple nine patch block. I just made new blocks, match the original fabric as much as possible, use a backing on the new blocks that I could sew around like a pillowcase, right sides together than turned right side out & appliques the new blocks over the worn ones.
It had been one of the first quilts I made 20 years ago, didn't know much about quilting/fabric, etc. Luckily the backing & batting had held up & just needed a little patching. But she was sentimental about it, making a new quilt would have been easier.