OK, you decide where people are getting it from, here is the data from KenPom:
Year - Defensive Eff - Offensive Eff - Finish
24 - 109 - 7 - 1st round
23 - 68 - 17 - 2nd Round
22 - 36 - 5 - 1st Round
21 - 35 - 68 - Missed Tournament
20 - 52 - 24 - No Tournament Played
19 - 8 - 14 - EE
18 - 22 - 24 - S16
17 - 7 - 12 - EE
16 - 39 - 5 - 2nd Round
15 - 1 - 6 - F4
14 - 32 - 14 - CG
13 - 88 - 38 - Missed Tournament
12 - 7 - 2 - Championship
11 - 16 - 8 - F4
10 - 6 - 22 - EE
Only 3 times in the first 10 years did we not have a top 25 defense, and only the 14 team made it past the 2nd round. We haven't had a top 25 defense since 19, and coincidentally, or maybe not, we have a grand total of a single NCAA tournament win (yes I know one of those years there wasn't a tournament). Conversely, only twice in the last 15 years have we not had a top 25 offense, and we missed the tournament both times. Just in the last 3 years, we have had 2 top 10 offensive effeciency teams, and neither of them won a game in the NCAA tournament, despite both being top 4 seeds. But you can't look at those numbers and not realize that the defense has been the major problem in the last 5 years. Of course, you could also watch the games, and even without the data to back it up, know that defense was the problem.