In the mid 1990's the government mandated that children's programming be educational.
That killed every good cartoon on network TV. Cable isn't subject to those laws. Corporate greed is killing those shows though for the reasons you listed. Also, cable just isn't a big money thing for the average show. They don't have the budgets that network shows have.
I buy box sets of the good shows so my daughter can watch them when she wants. And the best part is no ads and there are rarely still existing products so she's not being sold anything even passively.