They are about 14” too long.

A gusset doesn't protect against damage; it alters the pattern to allow the pants to have a greater range of motion. If they're tearing out catastrophically before the fabric is worn, then a gusseted design might help. If the material is wearing thin and then failing, then you need a design that has better, more suitable material. (For durability, I prefer cotton-poly or nylon-cotton blends. For extreme durability, there's also a few kevlar-cotton denims available, but there are no manufacturers I know of using those for shorts.)

FWIW, loose doesn't actually equate to good range of motion. If you want the best possible range of motion--regardless of material choices--the crotch of your shorts needs to be as high as possible.