The single most expensive thing that happens inside luggage is not breakage. It is a damp item spending nine hours pressed against everything you planned to wear.
Damp does not stay where you put it
A wet swimsuit rolled in a towel feels contained and is not. Water moves by capillary action through whatever it touches, and a packed case is nothing but contact — layers under pressure, with no airflow and often a warm hold. Nine hours of that is enough for mildew to establish on cotton, and the smell that results does not wash out on the first attempt. The same mechanism applies to a shampoo bottle that has weeped a few millilitres, and to shoes worn in rain. None of these are dramatic failures at the moment they happen, which is exactly why they are not caught until you unpack.
Two pouches, and one rule about which way things travel
A wet-dry bag with a sealed compartment handles anything actively damp: swimwear, a rinsed shirt, a towel you did not have time to dry. A separate laundry bag handles anything worn but dry, which needs containment for a different reason — not moisture but simply keeping worn clothes from being repacked among clean ones and losing track of which is which. The rule that makes both work is directional: things move from clean storage to worn storage and never back, no matter how briefly something was on. Shoes travel in their own bag for the same reason, because a sole carries whatever the pavement had on it.
Two pouches and one rule. It is not a sophisticated system, which is why it holds up when you are tired.