I recently read The Precipice which advocates for longtermism. I'd recommend this substack author read that book as it deals with the objections raised here.

It's true that longtermists view climate change as relatively less of a threat than other existential risks. The reason is that climate change seems unlikely to literally make humanity extinct or to trap us in an unrecoverable and inescapable bad position. Plus, climate change is relatively slow moving compared to other existential risks. The book does better than I will be about to do here in explaining this

I could see a grease fire on my kitchen stove and decide to put it out even while acknowledging that a fire is relatively less important than villains abducting me and my family and torturing us to death.