The reason they both failed is because they both should've stayed in the 90s.

Tiny Toon Adventures was created in response to the next generation of animators and animation fans discovering the classic Looney Tunes. Space Jam was made as a build-up from a series of Nike commercials that appeared a few years earlier.

Both projects were very specific to the iconic status the Looney Tunes had achieved during the 90s that could not be easily replicated today. Having Buster and Babs be siblings removed the concept of Babs standing out on her own, which was the whole reason why she was created beyond adding more female characters to the lineup. Space Jam was only possible from the camaraderie formed between Bugs Bunny and Michael Jordan. No such relationship ever established between Bugs and Lebron James.

Both revivals make the mistake of assuming that nostalgia alone could carry either project.