Using pixel coordinates for 2D space is like sizing web elements in pixels - it's just plain wrong and will look vanishingly small on future higher-resolution monitors.
Pixel artists would (and still continue to) consider every individual pixel, performing anti-aliasing by hand. Animations would be timed in relative to the (fixed) framerate, leading to optimal smoothness.
Reaching this level of fluidity is only recently possible again, at the cost of vastly higher hardware requirements. Most people haven't even experienced this, because of the suboptimal period we have been in for some time now.
You win some, you lose some.