The create a character was bad, the DS was incredibly limited to do a full blown mainline Dragon Quest game, and it was a major major step down from DQ8 which is one of the high points in the series. Sidequests were terrible and the combat was also fucked with which is something that every other dragon quest didn't fuck with because it was perfect.
it also had DLC which has now been removed since the server for DS games is dead.
So 9 is hated in many circles.
11 has so much polish mostly due to 9. They did not want a repeat. Dragon Quest is like if Ultima didn't stop releasing games or if Heroes of Might and Magic was still a thing. It's held to be something that sacred in Japan.