I am not sure what I expect, but "plastic garbage bags" just seems so anachronistic for a city in the distance future with flying cars and immortality!
This is exactly the point of cyberpunk dystopian fiction. What would it look like if a society was allowed to just run wild on hypercapitalist NIMBYism for a century? There is this idea that despite great technological advancement, we seem unable to solve basic human problems.
It doesn't at all seem surprising that mountains of trash would be everywhere in Night City. Imagine the Naples Waste Management Crisis but stretched out to a century - where public waste management is infiltrated by powerful business interests and criminal gangs, who exist openly and with impunity because the police is so underfunded they can't do anything about it.
Honestly, given the projected timespan, I think they were a bit conservative on the trash bags. I expected to see much more hazardous toxic waste in closer proximity to human settlements. I expected to see more terminally ill and dying people in the streets because they can't afford the treatment for lead poisoning and it ain't covered by health insurance.