The EC recently issued some new advise which implies that border control should no longer be a thing within the EU because, with some small exceptions, the situation is pretty bad just about everywhere and imported cases no longer make much of a difference in a situation of widespread and diffused domestic transmission in almost all countries. Of course, it's not a good thing that even countries which had low case numbers over the summer are now exploding with contagion, but elimination was never the strategy of any European country in the first place. So, what's happening now shouldn't be coming as a surprise to anyone.
The moral of the story? I think that the most likely development of the situation is that most of the developed world will eventually divide into two big bubbles, the COVID and the no-COVID ones. The latter will be shared among countries which went for elimination right away and succeeded or are about to succeed in it. Think China, Vietnam, Thailand, New Zealand, Australia... The former will be for everyone else. And coming across from the infectious bubble into the clean one will be subject to quarantine, tests, QR codes and whatnot else. Hard enough to be a deterrent to the vast majority of the travellers.