Isn't the concept of herd immunity a bit absurd?

You misread. (And it is sort of cute to be accusing me of throwing the shade in this thread.)

I have stated, very clearly, that IF their planners not also considering futures in which they cannot maintain their low levels forever, THEN they would be being very “unserious.” If they are not very nervous about their approach happening to break down just as influenza picks up to, then are are not as worried as they should be.

To the degree that they are behaving as if they have already won, and are not considering what a future in which SARS-CoV-2 is an endemic virus across the world looks like for them, I believe they are dropping the ball.

More power to them for having, for whatever reasons, been in a position that travel restrictions coupled with aggressive contact tracing and isolation have been able to keep rates very low to date. Best wishes for them being able to maintain that for however long such is required. And sure hoping they are prepared for that not succeeding.

My advocated positions have been written many times in this forum. Here and here for example.
From the second -