The old guy in Bakersfield was right and you gave up too easy. A router cuts one width, one depth, and the second the plywood is a hair undersized your shelf is rattling around. A hand cut dado you fit to the actual board, shim it with a card because plywood is never a true 3/4, and that shelf stays put for 30 years. The quiet is not the point either. It is that a backsaw and chisel never blow the shoulder out on oak veneer ply. Your tear out gripe is not a router problem, it is a router problem you signed up for. Slow down and score the line with a knife before you cut and half of that goes away.