Well, our global society is going to collapse very soon. What possible reason to not be alarmist could one have?

Seriously; our global civilization is in real danger of collapse in the next fifty years. I do see no reason not to panic or be alarmist?

I find it strange however that people are still able to actually ignore and deny the slew of icebergs we will be hitting in the next years; how can one be so delusional? Is it willful?

I think to a point it is. The idea that all of our oh-so-normal lives with hot showers that every human since the beginning of time enjoyed is coming to an end. And emotionally we just cannot deal with it; it's too big for us to grasp. And so we shut down that part of the brain and just suppress thinking about it.