As often in life the picture isn't black and white. The way I see it: Most people (~ 80 % or more) are decent. However we have egoists, narcissists and opportunists in our society. Unfortunately our current economic and societal system cultivate this sentiment and destill the most reckless undividuals into the highest roles (corrupt politicans, billionaires) where they assume everyone's jusg like them (who likes to see himself as outlier?) and hence make rules as if we were all assholes. With the benefit that it justifies their shitty behaviour... becaus ,,everyone else would do the same in my position". Well I say most people won't.
Durint COVID 10 - 20 % assholes where completly sufficient to empty stores out of greed (there never was an actual supply shortage after all). I once saw a woman in an expensive SUV carry a whole trunk of toilet paper to her house... which of course is anecdotal but fits my narrative.
On the other hand I saw many more people taking care of each other when going into isolation for example... in crysis the majortiy deepens its cooperation since it always more efficient than wasting ressouces in competition imho.