I think its pretty unlikely that someone else would have managed to overturn any of the demi-urges.
Yes all of them are stuck in some fashion, living their happily ever after being busy ruling 1/7 of everything in creation.
But they are also immensely powerful. Mottom gave us a pretty clear idea of that when she casually explained
how her entire palace were constantly being held up by her force of will alone.

And i think its unfair to state all the other demi-urges dont have their own goal.
Mammom did seem to have fallen into a senile state from his retirement.

But Mottom were busy conquering new worlds to feed her empire.
While SD is very clearly occupied either making a new generation of potential succecors, or managing squabbles between the 7.