Then, finally, all the actors record their lines. Those lines get edited and cut into an audio play, basically like an episode of an old-timey radio program without any sound effects. Then the producers meet with the animators and decide how they want each scene to look. That leads to an animatic, which looks a little like a flipbook, only much more expensive:
Also known as the "Fuck it, have the intern do it" phase.
Then, after yet another round of fucking notes, it's shipped off to Korea to get fully animated and colored. There, dozens of animators grind out tens of thousands of drawings. Other than the wages being roughly a third of what American animators make it's not nearly as sweatshoppy as it sounds (although we can't speak to the quality of the North Korean animation studios that helped bring you The Lion King).
When they get the episode back, which usually takes about four or five freaking months, they add the sound effects and music, typically completing the production process two weeks before the episode airs. That's anywhere from nine months to a year for a single episode, which takes less time to watch than it does to return a bag of socks at Walmart. You can make a freaking human being in the time it takes to create that episode you had playing in the background while you were microwaving a Hot Pocket.
And they can create another episode in the time it takes you to digest that Hot Pocket.
Now, it's true that shows like South Park cut this way down by going with an intentionally rough, low-budget look (and we'll get into that in a moment), but most forms of animation involve a staggering number of man hours, if for no other reason than the medium inherently requires many more steps than a live-action production. If you get back an animated scene only to discover that it's hideously drawn and the jokes aren't working, you can't just go reshoot it -- you have to wait another four or five months for it to be reanimated.
"Wait," you might be saying, "I thought this was all done with computers these days?" Well ...