Aside from the difficulties of getting everyone in the world to agree that the first three weeks of February during a leap year are observed through social distance, it doesn't seem like it would be as bad on a recurring basis as it is during an emergency like this. You could plan for your self-isolation in advance, so there wouldn't be a rush for supplies the way there is now; you would already know not to schedule anything for February; you'd probably still have to solve some money problems for a large number of people, since being able to WFH probably anti-correlates with living paycheck to paycheck.
If you could actually eliminate -- or at least, dramatically reduce the incidence of -- common colds and seasonal flu through such a scheme, it would probably be worth both from a QoL standpoint for the everyone in the world (would you trade 3 weeks of cabin fever every four years for never having another actual fever?) and from an economic standpoint (three weeks of predictable low productivity is almost certainly better than the unpredictable constant costs associated with illness and death).