Making cartoons is expensive.
Since Netflix has cartoons from other networks to fall back on, they can use their resources to make quality cartoon, especially since people give them money directly.
Meanwhile networks keep getting less and less money due to people watching streams and pirating instead of watching TV, not to mention less and less people buy merch.
Thus they have less resources to invest into original content and need to play it safe.
Does not matter what they air, because barely anyone watches. Services like Netflix give the networks only a small cut of the profit for airing their shows. This is why Disney wants to start their own streaming platform.
I say we still have it better than in the days of Hanna-Barbera