Eventually there will be a heat death of the universe, so that technically makes all existence 'meaningless' if you consider an ending to make everything before it meaningless.

Before then though, there will be a lot of existing going on for living beings, who fill their lives with meaning and joy and connection while they remain alive, and we'd rather like it if our environment wasn't a complete garbage fire while doing so.

Technically, we can. We probably will be able to do that a few hundred years from now and a few hundred years is nothing to something like the sun

You can make any question existential enough to void everything of meaning. Nobody cares about being effortlessly technically correct, they care about effort to correct something immediately material and consequential. "We're all gonna die so who cares?" Is the doomerist get out of jail free card to excuse being a part of, or a tool of those creating the problem. May as well not voice any opinion at all, because it won't be remembered forever. May as well just commit suicide because your relationships and your ultimate impact on the world and humanity through your existence is pointless because The Universe will end at some impossibly distant point in the future beyond what we can even pretend to understand as a scale of time. What a useful observation.