We should not rely on appeals to authority, those expert epidemiologists didn't do much better.
People interested in truth invite criticism: "Please give me contrary evidence! Show me I'm wrong!"
"We tried to prove this hypothesis wrong and could not" is the main thing you want a study to do. Having everyone try to prove your hypothesis wrong, and failing, is the main way that science advances.
The first step is Observation. Sometimes split out into Observation, then Research.
Then comes the formulation of a hypothesis.
After that is constructing a way to test the hypothesis. Not to prove it wrong, not to prove it right, but to test it.
There's more after that, it's an iterative process and a single test of a hypothesis isn't always definitive, often it is not. But "Prove me wrong" is not the starting point.
You accomplish very little trying to prove a hypothesis wrong, because most are.
The p-value of a scientific study is the probability that the given data would have been observed, given that there is no effect. Hence why small p-values can be associated with the success of the alternative hypothesis (i.e. what a scientist actually thinks will happen).
You can't prove an hypothesis is correct. All models are temporal until they are disprove.
But is it correct? To find out, we need to try to invalidate it. Try opening the can without tapping it first. If the Coke doesn't spill, the hypothesis is clearly wrong. It the Coke does spill now, it's quite strong evidence in favor of the hypothesis.
How did you arrive at this assessment? I've been following this since the end of January, and every expert I've heard gave sound and very good advise based on the available evidence at that time. Some of them might have made some disputable trade-offs, for example the Swedish lead epidemiologist, but overall there was a lot of agreement and the recommendations were excellent.
Okay, maybe there are a few outlier countries like the US and Brazil where there might have been political muddling of the expert messages. Be that as it may, in general the advice from experts was not only good, most countries also succeeded in controlling the spread of the virus based on it. (And not every country needs to implement the same measures to be successful in that, it's more about a mix that works in that country.)
The non-expert Michael Levitt, predicted at the same time, by fitting 3 parameters of a Gompertz distribution (And no other knowledge), that Sweden will have 5000 deaths on 1-July if things continue as they were when he made the prediction (that is, no WHO recommended lockdown).
I'll leave it to you to lookup the Swedish death count on 1-July to see if the expert epidemiologists from the WHO had a better idea than non-expert Levitt. (But I'll give you a hint: It is mid september, and Sweden has ~6000 deaths).
The WHO advice was much better than what Swedish advisors came up with.
Besides that, I was not talking about WHO experts but about experts in general. Every country has them, and they supply the data to WHO.
Last but not least, you cannot evaluate a model on the basis of a singular prediction.