The Doomsday Clock has always been political rhetoric.

Why is that a bad thing?

Normally, one might make the charitable assumption that an organization with a name like "Atomic Science and Security Board" does something other than spout political messages. It seems plausible that they might be a body of experts assessing the relationship between the world's nuclear powers and communicating their analysis through an easy to understand metaphor. Unfortunately, they chose a metaphor that holds them accountable, and now that they're run out of metaphorical hours and minutes with which to communicate deterioration in the situation, they make a mockery of themselves with every press release.

The situation is grave, but the Doomsday Clock is a joke.

How would you suggest they communicate their point?

As an explicitly partisan organization

How is “I don’t want civilization to end” partisan?

I would suggest that they ought to have focused more on the threat of global thermonuclear annihilation and less on climate change. There is no shortage of focus on climate change these days, and the metaphor of the doomsday clock was much a more powerful and literal one when focusing on such weapons (the idea of a clock at five minutes to midnight being: the clock could start up again at any moment, and in five minutes, you would be dead).

Folding "climate change" into that makes only slightly more sense than augmenting a tornado warning system with information on the skyrocketing national debt. Mushy metaphors do little to change the world.

Perhaps the clock's maintainers sought to fend off irrelevance; no one pays attention to nuclear weapons as a threat in the West (barring occasional North Korea flare-ups). If that is the case, however, I fear that this has only made things worse.

These are tied though. Climate change will displace populations and ramp up pressure on governments, making conflict more likely.

Why hollow?