My wife worked for a cloth upcycling association (finding sustainable future for discarded clothes).

Reality is, there is just 10x more thrown out clothes in the west that any third world country on earth could need, same for shelters.

Associations distributing clothes to developing countries / shelters are filtering tightly what they accept.

In short, the vast majority of thrown out clothes in the west are just crapwear that not even the third world want. There are entire pipelines of filtering and sorting to only keep and distribute the good quality clothes.