In the beginning most western countries were following advice from the Imperial College of London, which assumed that the virus would spread through populations with minimal deaths and all that was necessary was to protect the most vulnerable populations eg. nursing home residents, and to minimize the pressure on hospitals, especially ICUs ie. flatten the curve such that the most serious cases occurred over a longer time frame so additional critical care units wouldn't be needed.
The problem is that this guidance was based on many assumptions that turned out to be wrong. They assumed that China had overreacted to the virus, that more people had actually been infected than China had admitted and that explained why they had had to build 2 new huge critical care hospitals in Wuhan. They assumed that this virus only spread as quickly as influenza ie. they got the R0 wrong and assumed it was closer to 2 when it was actually between 5 and 8. They also made the assumption that economies would be better off continuing as usual and for everyone to just endure the deaths as herd immunity was built up -- leading economists came out pretty quickly and tried to tell everyone that this couldn't happen and basically tell these guys to stay in their own lane. And from my perspective they made a huge mistake by assuming that SARS-CoV-2 was just a respiratory virus, since most coronoviruses only cause the common cold. It wasn't until there was time to do autopsies around the world that scientists understood this virus actually affected the blood and consequently patients would die of things other than respiratory arrest and those who survived would have lasting damage. Early on people who died from heart attacks and strokes were just counted as heart attacks and strokes. There are many more but they got the most important things wrong.
It wasn't until the virus hit Italy that western governments started to re-think this guidance and not all did. It took a long time for countries like Sweden and the US to get on a different path. In the mean time, many smaller countries had actually eradicated the virus within their borders. Countries like Mongolia, Vietnam and Taiwan started from the assumption that this virus was something new and they didn't really have enough information about it to try to dance around it -- but they did know they didn't have the resources to set up thousands more critical care beds so they just had to stomp it out.
"Flatten the curve" was just another way of saying they were going to let some people die or become critically ill but that they didn't want too many to be critically ill at the same time because there weren't enough resources available for that. Eradication is actually the only feasible goal and vaccines are just another tactic to accomplish this. They have to stop the spread of the virus from person to person so that the virus can't find a new host and eventually dies out. This could have been accomplished through masks and physical distancing and closing borders but since so many people refuse to go along with this in some countries and because the virus has already been spread so widely, vaccines have to be used instead. It's still not clear whether this will be enough because vaccinated people will probably still be able to infect others. Current vaccines only prevent patients from becoming critically ill.
For what it's worth, during the Black Death, they assumed that just shutting sick people into their homes would be enough to stop the pandemic. Eventually they too realized they had to close the city gates and quarantine any ships coming in. This did cause economic hardships but short term economic pain was preferable to ongoing economic devastation from the pandemic. I do agree with you that convincing people to stay home when ill is the best thing to come out of this -- in most countries we were assuming that deaths from viruses like influenza were inevitable and acceptable. I hope this is a permanent change because this won't be the last novel virus we have to deal with.
