A moisturiser does not nourish your skin. Nothing applied to the outside of the stratum corneum is feeding anything. The layer it sits on is made of cells that are already dead, which is not a flaw in the design, it is the design.
What a moisturiser does is manage water. There are three ways to do it, and almost every product on the market uses some combination of the three, even when the marketing only mentions one.
Humectants attract water and hold it. They are water loving molecules that draw moisture into the upper layer of skin and keep it there. Glycerin is the most widely used example. Humectants raise the water content of the surface layer, which is why skin feels plumper and looks smoother soon after application. The effect is real and it is also shallow, in the literal sense. It is happening in the top layers.
Emollients fill the spaces between cells. When the surface layer is disordered, the corneocytes do not sit flush against each other, and the surface becomes rough and catches the light unevenly. Emollients settle into those gaps. This is most of what people are responding to when they say a product made their skin feel soft, and it is why the effect is noticeable immediately.
Occlusives slow evaporation. They form a layer that reduces how fast water leaves through the surface. This is the mechanism that directly lowers transepidermal water loss, and it is the one most closely tied to the barrier itself. Petrolatum is the most effective occlusive known, which is why it keeps appearing in products that look nothing like each other.
Three points follow, and they are why this is worth understanding rather than just knowing.
The first is that these three mechanisms are not interchangeable. A humectant on its own, in dry air, can raise the water content of the surface without doing anything to stop that water leaving. An occlusive on its own holds water in without adding any. The combination is usually what works, which is why well built moisturisers contain more than one type and why arguing about a single hero ingredient misses how the product actually functions.
The second is that feel and function are different things, and feel is much easier to sell. The immediate softness of a product comes mostly from emollients and humectants. The slower work of reducing water loss comes mostly from occlusives, which often feel heavier and less pleasant. A product engineered to feel wonderful in the first thirty seconds and a product engineered to reduce TEWL over eight hours are not necessarily the same product. The first is easier to like. The second is harder to notice.
The third is that the skin is doing the actual repair. Reducing water loss creates conditions in which the skin's own lipid production and barrier assembly can proceed. That is a real contribution and it is not the same as the product rebuilding anything. The claim that a cream repairs your barrier attributes to the cream what the skin is doing.
None of this says anything about which product suits you. Air humidity, climate, how often you wash, what else you apply, your age and your genetics all change the answer, and a formulation that works well for one person can sit badly on another for reasons nobody can predict from the label.
What it does give you is the right question. Not what is in it, but which of the three things is it doing, and is that the thing my skin currently needs.
A moisturiser does not feed your skin. It changes how much water leaves it.