A lot of places were bad before crack, Detroit, inner city LA, Washington, most of New York, and things had gotten very bad during the 1970's. The economy was slowing, white flight was a thing, and scum like Frank Lucas had caused a heroin epidemic even before Crack came along.
Crack was more a symptom of the wider problems, namely the slow collapse of the American heavy industries which disproportionately hit the black inner city communities. This in turn caused an economic collapse in these areas which in turn led to people turning to drugs as a way out.
The Vietnam war had let people like Lucas get direct access to the Golden Triangle which to quote American Gangster let him, "Sell shit that's twice as good for half as much." Alongside this you had the rise of the South American Guerrilla movements who were happy to sell vast quantities of cocaine to finance themselves. That led to oversupply and the need to create a new product to compete...result crack.
Truth be told Crack isn't that much worse than heroin or standard Cocaine but as the drug of the streets, it was a target that could still ignore the cocaine parties on wall street.
Without crack heroin probably remains the big thing, with cocaine as the "rich man's drug." You'd almost certainly still see the Reagan era crackdown, which in turn would be handled badly and target the victims, throwing thousands of black men into jail for possession. That in turn still lets the gangs rise on drug profits and prison recruitment, its just smack stays the boogieman until Meth comes along.
The combination of a badly mishandled drug war and the desire of certain groups to make money off the stuff was always going to happen, the only real possible difference was what drug caused the epidemic.