>>50218339GameFreak was abhorrent at optimizing for DS development and refused to accept any help from Nintendo, even with a delay to make sure the games were functional and finished they still didn't give a flying fuck about making it run as smooth as Gen 3.
Remember, TO THIS DAY, Gen 3 are the ONLY core games that ran at a seamless 60 FPS with no loading whatsoever outside of multiplayer communications.