>What happens if truly nobody wants those clothes
In theory companies would eventually be forced to produce less items nobody wants, although this is just an additional incentive in that natural process.
I would think the incentives to produce things no one wants would already be pretty low.
Overproducing is often cheaper than losing sales because of the fixed costs of producing a batch and the externalities of destroying your inventory not being priced in. Some brands also find it more interesting to destroy stocks than reduce prices because it protects their brand values. Well, now, that's illegal.
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That doesn't really make sense, losing your whole investment is already a strong incentive to not produce something you can't sell.