The trick is that while they are cutting corners, and the scene may have LESS animation, with competent direction it is designed to look more dynamic and impactful that a highly fluid animation that just sets back and watches the whole thing from a single perspective the whole clip. Adventure Time has 3x the frames of an episode of an anime crammed into half the runtime, but a lot of that is wasted watching two characters stand there and talk about hipster bullshit with occasional shoulder shrugging or walking around. Actions that don't advance the scene and don't stick in the mind of the audience.
People don't watch pic related and remember the still frames, zooms, and close up face shots. People watch pic related and remember that it was hype as shit.
Another example is Evangelion. Evangelion has a LOT of budget saving going on there. Covered mouths, still images that last for 10 seconds or more at a time, the elevator scene, etc. They literally ran out of budget by the end. But the scene direction and visual composition was so on-point that even the still images are iconic enough you could put them on a postcard. The show is 25 years old and still looks great, which is no small feat.