No win possible?
As Roo states the WHO are a coordinating entity and based their comments on available confirmed information. Can they really be blamed for not saying it is China human to human transmission at fault because Taiwan said so.
Arguably China could have been assumed to be lying but the WHO explicitly stated that China had advised there was no evidence, they didn't say definitively that there was no evidence.
The same with the Pandemic status which iirc basically went through a process of x number of reported infections, something to be concerned about, now we would class it as an epidemic but not enough confirmed victims over a large enough area to be a pandemic, those criteria have been met and it is now officially a pandemic. They not only set their criteria for each stage but explained why a stage hadn't been reached at a given point in time.
The there is the whole 'Shouting Wolf' syndrome. If they had gone earlier with the pandemic status more live almost certainly would have been saved and number of infections would have been reduced. They would then have been accused of over reacting then in the future when they call a pandemic they would be ignored, except as a result the wolf and all his / her friends turn up and have a jolly good time ripping everyone's throats out because everyone thought it was just another false alarm and not as serious as was being made out.
America is a perfect example of this. The number of cases and deaths are lower than expected due to lock downs but a number of Republicans are saying the small number of cases show the lock downs were an over reaction rather than an effective method of dealing with the virus spread. Next time a lock down is called how many people will take it seriously?