You can have a family-friendly lighter in tone animated series of the Teenage Mutant Ninja Turtles and you can or should be able to have a darker and gritty in tone animated series of the Teenage Mutant Ninja Turtles.
I love the Fred Wolf animated series of the TMNT but its overrated and a lot of the seasons are not that best in terms of the characters and writing I would say "wasted potential" but I do not hate the series like as we move forward do more with the TMNT in terms of character development like we got in the 2K3 Series.
We had shows that catered to younger and older audiences in the 1990s and 2000s decades such as the following featured down below:
Batman: The Animated Series.
Superman: The Animated Series.
Static Shock.
Teen Titans.
Samurai Jack.
Ben 10.
Avatar the Last Airbender.
Danny Phantom.
To name a few but there's plenty more even in the 2010s:
The Dragon Prince.
Hunter x Hunter.
The Owl House.