>>98742517If I had to say, a smaller cast of characters works best. Gives the writers less room to stereotype the characters, so they have to actually try to develop them
(to a certain extent depending on the cartoon, a lot of people get stupidly upset when they think their cartoon can just avoid this part all together for some reason) and keep them consistent before the viewers can call bullshit on stagnation and degradation. Of course this may never last, just look at Spongebob or The Simpsons.
A large cast of characters these days just doesn't cut it for most cartoons, because the writers will never get all the time and resources needed to develop beyond the tropes (which may or may not be accidental) they slapped on to their characters outside a hand few, but then those hand few will just look like creator pets due to the other characters never evolving. A large cast can work wonders, though, it's just that the writers are probably bound by a variety of restrictions.
And if it ain't restrictions and it is just writers incompetence, then all is lost. 
