> Their reasoning is that if the only things you can do are China style lockdown or nothing, then the disease will just resume exponentially growing the second lockdown ends, so it's pointless to do it at all.

Before quarantine we had many people infected not knowing they are infected, spreading the virus around.

After a few weeks of quarantine the ones infected will be known and separated from the rest, so the virus should be stopped. That is assuming the quarantine is strict.