Initial response to isolated infections requires a different response to that you give an entrenched pandemic. When it always comes back from multiple countries and is initially undetectable complete shutdown trace and contain simply won’t work.
Not sure why every country couldn't do the same to isolate incoming infections.
This isn’t really tenable if you want a functioning economy, and cases will slip through.
And it seems a pretty common sense preventative measure since a 14 day quarantine isn't too onerous.