Well that's obvious. No country plans to remain isolated forever; only until a significant population has been vaccinated. Fiji are opening up to the world on December first now that 90% of the eligible population are vaccinated. New Zealand will remain closed until April because their vaccination was delayed by letting less developed nations get first dibs to the vaccine.
So it's perpetually locking you into travel bans to be effective, which is in itself very harmful to a country in today's world.
It only works if everyone did it and you succeed in killing the virus. Right now that is no longer possible because the animal kingdom will keep it alive.