Earlier quoted context omitted.
Supply and demand is one driver of economic pricing, but not the only driver. Efficient pricing is a complex topic and not as black-and-white as it seems. As demand falls, the price may be expected to fall, but there is an inelastic limit set by material, labor, transport, and taxation cost. A company may elect to decrease their profit margin per sale to offset increased costs, but there is only so much margin to eat…
This is just semantics. If it becomes untenable to supply a good at a given price, the supply for that good decreases. Then supply and demand reach equilibrium. Supply and demand doesn’t mean that either or both supply and demand remain constant. Both supply and demand change depending on the price.
But that's a massive oversimplification. It's like saying programming is "just typing". Technically, sure; accurate, no. There's latency in the real world. Bad actors. Information asymmetries. Regulations. Monopolies. Stuff you can't do without and can't even always decline (ambulance ride for an unconscious person). Fake news about a supply crunch changes demand without changing supply for a while.