Of course they do, especially when the number of people is ambiguous or when they are speaking about someone titled as a profession such as "I went to the doctor and they said..."
It is all a manufactured situation used to push hate and attack the marginalised. Singular they has been around for a very long time and there were options before they was they, not to mention in all the other myriad languages in the world.
First, the term hysteria is from a fairly mysoginist root, so maybe consider whether that is the best word here.
Second, for all the 8 million plus people killed by COVID it wasn't hysteria, they died. They didn't have the sniffles, they died. Dead. Not alive. There isn't really a lot that is worse as an outcome from a respiratory infection, however we have that too! Tonnes of people who didn't die have long covid symptoms, strokes, heart attacks, various thrombotic events, loss of function, and additional complications in the rest of their medical issues. On top of that plenty of people had parents, siblings, children, friends, or other people important to them die or become disabled.
Third, digital dependence? I mean, we were moving in this direction for decades before covid. It used to be nobody had phones at all. My partners grandparents remembered the house down the block getting a telephone and went over to see it. They didn't have electricity. That was less than a century ago. The ramp up of technology over the last century has been insane and accelerating that whole time. In 2004 the coolest phone was a Motorola RAZR flip phone with a terrible 0.3 megapixel camera but a stunning 176x220 pixel display. In 2024 a Pixel 9 has a 1080x2424 display and a 50, 48, and 10.5 megapixel camera. The comparison of a rifle and a spear feels appropriate. We were already heading towards more technology in our lives, it just because super noticeable during lockdowns as it accelerated a little more for a couple of years and it was more obvious.
Fourth, why the quotes around expert? There is such a thing as an expert. Someone who knows more than me doesn't have to know everything to keep knowing more than me. They can be wrong and learn new things and change their mind all while remaining more informed than I am. In fact, being an expert in a field means doing that constantly. Being at the frontier of knowledge means holding your beliefs more tentatively as you are more likely to change your understanding than an uninformed average person. The fact that they didn't know how good masks would be at the start isn't an indictment of their expert status, it is their first guess given previous knowledge. What they did after that is what makes them experts, namely changing their minds when new evidence came about.