In order to do their job effectively, the WHO needs access to populations that live under a dictatorship. You can very reasonably argue that the WHO should be

In order to do their job effectively, the WHO needs access to populations that live under a dictatorship. You can very reasonably argue that the WHO should be more open and transparent, but they need to be very careful about how they operate inside of authoritarian states. China could simply pull out of the WHO and then the organization would lose visibility into a huge chunk of the world population. It's a difficult balance to strike. That's just realpolitik. Instead, the United States is doing China the favor of pulling out so China doesn't have to. This gives China more control over the WHO. Ultimately, as the US abandons its position of global leadership it allows China to take on the mantle. This is a boon to the Chinese communist party. If Obama had pulled out of the WHO during an epidemic I would think this is a supremely irresponsible decision. Though I will admit that if it were Obama making this decision I might suspect there could be factors that aren't known to the general public, rather than just narcissistic boneheaded idiocy.