I think this is an overly reductive class analysis of Scooby Doo. Scooby Doo villains aren't proletariat; their schemes require far too much money and time for anyone who makes money off of labor. In addition, their goal is usually a position based around extraction: owner of a theme park, operator of a uranium mine, etc.
As for the gang, their parents are obviously bourgeois, but as children, they don't have control over those resources, or even particularly regular access to them. They live in a van rather than their own houses. Norville Rogers III, who comes from the richest family, is constantly hungry, and constantly reliant on others to provide for this basic need.
Scooby Doo isn't the bourgeois fighting the proletariat; it is an internal struggle between different factions of the bourgeois. The Scooby Doo villains are the nouveau riche, social climbers fighting to establish themselves and willing to play upon the fears and taboos of their betters to do it. The gang represents the next generation of the already established bourgeois, who wish to maintain a status quo that promises only that it may have space for them. There is no hero in Scooby Doo, only the cold reality of a fracturing class system.