"No specific evidence" is weasel-wording. I have family in China. Before the spread here in the West, people were buying up N95 masks and sending them to Asia because they knew what was coming.
I'm of the opinion that the advice to not bother with masks early on was intended to address an expected shortfall for medical personnel. That is, it was manipulation.
Is there specific evidence that vaccines don't cause long-term harm? And if in time, evidence shows that they do cause harm, who will be responsible? (in slovenia, all the vaccines were safe and effective, then we first stopped using astrazeneca due to clots and a woman dying, then israel said they don't work enough, and mandated a third shot, then a girl died in slovenia due to Janssen, and only mrna vaccines were recommended for young people, then sweden and denmark stopped using moderna, so we're down to one safe vaccine).
Even the stupidests little things, like sanitizing the living crap out of stuff, even before the mask mandates, was something that was 'true' back then, then the 'truth' changed, and we still had to pay for all the useless crap... we had mandated sanitizers in elevators, all the high buildings paid a shitton of money for them (because the dispensers were expensive then and hard to get), then someone though about fire codes, and "woops, remove them".
TLDR: the problem is not that science changes, the problem is, that we do very socially and economically dangerous and expensive stuff now by blindly trusting whatever the current scientific idea is, not thinking about "what if the science is wrong?" (eg. if covid is transmitted mostly by air and not by touching infected surfaces).