I think Sweden is taking a huge risk but it’s up to each country to try to manage the disease as best they can. If they can allow it to spread without breaching their health service capacity then who’s to say that ultimately that might not be the best decision in the long run.
The problem I can see with their strategy is the lag between restriction measures being implemented and the confirmed cases coming through (people showing symptoms and then needing hospital treatment) and whether it spreads to higher risk individuals. This is made even more difficult due to the high number of asymptomatic/mild cases ie You could start putting restrictions in place to control the spread but it could be too late as it’s spread more than you think and you’re going to breach your health service capacity anyway.
I honestly don’t think anyone will know the best solution/strategy for months or even longer. The only fact we know at the moment is we don’t have a vaccine and therefore this is around for a good while yet.
All countries can do in the meantime is try to buy some time in order for us to find out how to best to manage/treat the virus (or find a vaccine), whilst remaining within their health care capacity, without damaging the economy to the point whereby more damage is done to society than would be done by the virus itself.
Not easy
ps also, if it’s discovered that you can catch it again, there’s another layer to the mess which changes the dynamics again