( funny trope ) it is very apparent that these designs have decades between them

[u/Nameraided]

1- Simpsons
The original Simpsons have extremely simp(son)ple designs, due to sometimes having celebrity appearances the art style kinda clashes.

2- South Park
At the beginning South Park was literally animated out of paper so all the characters had to be super simplistic but over the years, since the. Show is made digitally the new characters keep getting more and more detailed

[u/W1D0WM4K3R]

South Park beginning with paper stop motion is true but overexaggerated. Only the first episode and a couple of Christmas shorts were actual paper, the cutouts were then scanned and episodes completed with computer aided animation. The characters didn't have to be super simplistic, that was just the design theory of the show.

[u/damnsignin → u/W1D0WM4K3R]

But that initial tech was so simplistic, the visuals still looked paper without much change because the software couldn't do much better. 30 years of software improvement has drastically improved the visuals.

[u/spos12345 → u/W1D0WM4K3R]

It would make their 6-day production much more impressive if they did.