Analysis on The Future’s perspective in Tenet
Firstly a fundamental fact: what’s done is done. The future can’t do an ’assassinate the Hitler’ type of operation to revert the damage done on their environment, which is why they fought the war in TENET. It‘s a uniform decision by the Future, because it was what had to be done. There is no choice.
Which is why on the phone, either the Protagonist or Sator said that this was a war between generations. Tenet probably got to the female scientist that created the device somehow and compromised her, such that the Algorithm was split into pieces and sent backwards in time.
Secondly, what does the Algorithm really do? It sets the universe in reverse. The Algorithm destroying everything is just a theory, which is hinted by the Oppenheimer analogy. Oppenheimer feared that a nuclear explosion might destroy the whole world, which didn’t happen. The most likely scenario is that people in the present just won’t be able to move forward in time, without even realizing It, and the future would be able to live in decreasing entropy, however weird that may be.