The WHO screwed up quite badly. It took them two years to admit COVID was airborne–well past the time where the evidence was incontrovertible. A few months can be blamed on early uncertainty. Not years. This tweet aged quite badly:
The reason is a 60-year-old dogma they held that there were basically just two categories of non-contact transmission: droplets larger than 5 microns that fall out of the air rapidly, and small particles that can hang around for hours. But not only is reality not that binary, the 5-micron figure is just flat-out wrong, conflating two different figures from an ancient paper (the droplet threshold was supposed to be 100 microns).
In spite of all the obvious evidence, both empirical and theoretical, it took the WHO immense pressure to cave. And even at that, it was only in April of this year that the WHO actually redefined airborne transmission to be evidence-based. They could have done this decades earlier had they been more receptive to earlier reports that the dogma had been violated.
Not that I disagree with the point that hand-washing was an easy early precaution. But it took way longer than it should have to give better advice. And statements like the tweet above were just shameful.