I know this board likes to glorify the recent days of the big East but overall the conference did underachive in march. But most of that is due to the combined efforts of georgetown, pity, and notre dame.
You're not giving the Big East enough credit. When the conference added 5 schools and got to 16 it was the start of the second "Golden Age" of the BE.
Getting past the Sweet Sixteen (reaching the Elite Eight) is a hard thing to do, I personally use this accomplishment to judge teams, coaches, and conferences - I have for many years. Making the Sweet 16 is nice and reaching the Final Four is tremendous but I consider getting to the Elite 8 a very successful season for any program. Even the best teams have a hard time getting there.
In the 8 seasons since the Big East added the 5 schools (2006-2013) here's how many different schools from the major conferences made it to at least the Elite 8 and how many times combined they've done it (note: this has nothing to do with FFs and NCs, just E8s):
BE..... 8, 15
Big12. 6, 11
SEC... 4, 10
Big10. 3, 6
Pac12. 3, 5
ACC... 2, 7
In the last 8 years the Big East has had 8 different schools make it past the Sweet 16 and they've done it a combined 15 times. The Big12 and the SEC have done quite well in March too, contrary to what most would think. The ACC has done the worst, only North Carolina and Duke have made it that far - no other ACC school has made it past the Sweet 16 in the last 8 years.
Despite Pitt and Gtown not going farther than they should most years in the tourney, despite Notre Dame underachieving every year, and despite the bottom 6 schools doing nothing in March, the Big East has been very impressive in this most recent Golden Age - more so than any other conference.