All the old ignorant fantasies are being wheeled out over and over again. The ignorance about science and scepticism about people with genuine scientific expertise is scary.
Limiting contact is the only way to control infectious disease until vaccination is available. It was done in one way or another since the time of the Black Death. Eyam famously isolated itself in the Black Death to save others from suffering.
The SIR/SEIR mathematical models are used to model epidemics and, although imperfect, work well. They are what inform the degree and type of lockdowns required.
COVID turned out to be (somewhat) less morbid than scientists first thought based on the Italian cluster, but that was the data available at the time. Nonetheless if large cities like London hadn’t locked down, hospitals would have been overwhelmed and we would have had people dying in pain at home and bodies in the street. There is very little doubt of that.
If a new disease came along, it would be just like COVID at the start, little known and understood and possibly far more lethal.
And, yes, of course people would comply. There are a lot of people on these threads who are very brave retrospectively but were very fearful at the time. If you thought you might die untreated of a nasty new virus, you would do your very best not to!
We have entered a new superstitious age where science and scientists are not respected. It is sad.