So I'm replaying Leafgreen atm and holy shit why does this game feel like it plays so much faster than Sun and Moon?

I'm not even talking about cutscenes or anything, but mostly how everything just loads in faster, the animations for moves are quick, scrolling menus doesn't seem nearly as much of a slog, the text is faster, etc

Is it just that Sun and Moon are poorly made in terms of performance? Or is it something else?