Yanky55 (from page 1 of this thread):
Rashi in Rosh Hashana addresses your very point.
On Daf 32b D”H ???????? (top of the wide lines at the bottom of the amud) Rashi says: “???? ????? ??????? ?? ??? ?? ????? ?????” (“Once Yerushalayim was destroyed, the Chachamim saw no need to beautify it.”)
Sorry it took me so long to answer you, I had to find the exact source.