If they wanted to make a mature Scooby-Doo series literally all they had to do was show how four teenagers and a Great Dane survive travelling and living in a van while doing their usual mystery solving shenanigans.
I’m talking showing scenes of something bumping the van in the middle of the night while they’re sleeping shoulder to shoulder under a single blanket covering everyone. Scooby tumbles across the four of them and insists it was something outside, not him chasing a rabbit in his sleep.
In the mornings the guys wash and dress on one side of the Mystery Machine and the girls on the other. They shout theories over the van, occasionally getting side-lined by debating who’s setting up the gas cooker to make breakfast.
While Fred or Shaggy drives Daphne tests Velma with questions from textbooks so she can stay up to date on schoolwork. Fred always claims they’re students from a nearby city on a road-trip for a school project whenever they’re pulled over by the cops.
Each time they get paid for solving a mystery they stock up on non-perishable food that can be stored in the van (including Scooby Snacks of course!). Then they make a budget plan for stretching their money, fuel and supplies long enough to get to their next paid mystery.
Sex and drugs can be an underlining thing, but it doesn’t need to be a cheap source of humour. While they’re lounging in the back of the van Shaggy could be shown casually rolling a blunt while trying to convince everyone they shouldn’t venture into that abandoned office building the mayor insists is closed for repairs. Fred and Daphne sometimes insist that Shaggy, Scooby, and Velma go search for leads for a few hours while they’d stay at the van and “talk over some trap plans”.
On top of that, if they wanted to go dark mature they could add in backstories of the kids having troubled home lives, hence why there’s no concern for them being essentially homeless and dropping out of school. Also an explanation on why their parents haven’t sicced cops on them to bring them home.
Seriously, in the Scooby-Doo universe this is what constitutes being “mature and a deconstruction” on the typical premise. Not some edgy, holier-than-thou teens wearing Mystery Inc face-paint cracking flat jokes that are only relevant for this specific period in time.
