There are still packs available without a proliferation of zippers and do-dads, particularly those marketed to the ultra light crowd. One of my favorites has exactly one zipper, on a small, rarely used compartment. The main compartment is closed by a friction clamp on a cord - quite silent in operation. Many accessory bags use the same kind of closure.

I often will replace metal pulls on zippers with cord. This also will lighten your pack by, say, 0.2 oz, as well. Operating a well lubricated zipper slowly will minimize noise. Velcro is incurable.

In real life, my klutzy movements, belching, etc., drown out the sounds of operating zippers and velcro.