Complacency is just as dangerous as panic
In this case, complacency is much, much worse than panic.
This is very simple: you have 4 scenarios.
1) The situation is dire and you react very aggressively.
2) The situation is not as bad as people think and you are relatively cool.
3) The situation is dire and you are cool
4) The situation is not as bad as you think but you react very aggressively
Let's remember you don't "know" how dire the situation is, you guess, sometimes with good info, sometimes without it. If you wait too much to get enough info you might be late to react, that's part of the point.
1) and 2) are no brainers as the response matches what is required by the situation and 3) and 4) are what is called in statistics as Type I and Type II errors (when you reject a null hypothesis while it is true, and accepting a false null hypothesis). Most responses imply a trade-off between the costs of both of those.
In this case, it is obvious for anyone with two functioning brain cells, that the cost for 3 is higher than the cost of 4, so it is better to overreact than to underreact. You don't want to waste resources and cause unnecessary panic (keyword unnecessary) but if your choice is between "bad" and "worse", if you hesitate to pick bad just because it comes at a cost, you are an idiot.
Let's remember the overwhelming majority of the countries we are following here are not Somalia, Chad, Sudan, Venezuela, or Haiti. We are talking about relatively rich countries that can weather out an economic hit.
When you face a crisis you need to address the bottleneck first, and the bottleneck here is the medical system's capacity, in particular, the capacity to handle people with respiratory problems, meaning beds, nurses, doctors, and respirators are key. Overreacting does not harm you in achieving that (although it might incur in some unnecessary economic cost). Being slow to react does put more pressure on that bottleneck.