I get what you're saying, but Couples has had back issues almost his entire career. Frankly, if Tiger's swing was truly was bad on his body, then we'd see Adam Scott encountering the same issues, because AS has Tiger's swing at Tiger's peak.
AS is 34. Age may well catch up with him and he may well experience back issues a few years down the road.
Tiger's game was a function of the rules changes that allowed boxed grooves, I think in 1976. Driving accuracy doesn't matter as much, if you can just rip it out of a bad lie.
Now the grooves are more rounded at the face, but not v shape prior to '76 that made hitting out of the rough with spin was an art few mastered. So Tiger's game, as it was, is no longer optimized to the equipment. He is trying to change by moving to a power fade, so with a fundamental swing change, I doubt he will be as effective as with old grooves.
Scott has the same swing plane and motion, but not with the same excessive-ness in delivery, which is no longer well suited to the equipment. Scott is tall, so his longevity is certainly in issue. His delivery is more smooth, and I doubt highly he will ever jack himself up as I suspect Tiger did.