Do people who don't believe in God think life has no point ?

If you don't believe in an after life/ God. Then by default life has no meaning.

You are stuck for a lot of years just to die and disappear, why keep going and not just die ? "Nothing matters" anyways.

Isn't that just really depressing? Is it why most athiests on reddit spread negativity on life and hate that they are even alive?

It doesn't really make sense to ignore religion / God by your own free will. Just so you can suffer knowing there's no point.