At C2, in the English Vocabulary Profile,
the INFORMAL phrase ‘so much for’ + noun phrase is defined:
used to say that something has not been useful or successful
The Cambridge dictionary:
used to express disappointment at the fact that a situation is not as you thought it was
A search in COCA
1 . SO MUCH FOR THAT THEORY . 6
2 . SO MUCH FOR THAT . 5
3 . SO MUCH FOR THE THEORY THAT 5
4 . SO MUCH FOR ‘ NOT DOING 4
5 . SO MUCH FOR PEACE AND QUIET 4