Pandemics are - by definition - a global problem and trying to solve these with local countermeasures (aka, take care of the West and forget about the rest) isn't going to work: until such a thing is under control everywhere it might as well not be under control anywhere.
The current mess is there to a large degree because countries have been ignoring the WHO, not because they followed the WHO and their advice turned out to be nonsense.
If anything the WHO should have been more strict in their initial reading of the situation and I'm pretty sure that they have learned their lesson, but the prevention paradox is real and if they had cried 'wolf' too early they would have been abused by the same people that now claim that they messed up because they didn't react soon enough and strong enough.
From day #1 the WHO has been arguing for strong countermeasures rather than to slow-walk it to see how bad it was going to get because time lost will not be won back during a pandemic.
WHO Press briefing March 13th 2020:
https://www.youtube.com/watch?v=AqRHH6e-y6I
The WHO did not fail us, but politicians certainly did.