Peach trees are short lived 15-20 years. They prefer good drainage, so here in wet Oregon, we usually plant them on a mound. The trees don't look that bad, but you might have a soil test done. Your soil might be low in copper, or the pH might be off, or the tree needs better drainage.
As to pruning, you want to keep the center of the tree fairly open to allow air movement and sunshine to get inside. Lots of thing effect fruit load. Soil is only one of them.