Here are some numbers I put together several years ago, looking at whether blocked shots or diminishing power plays had more to do with the decline of offense.
Format is as follows:
Year - Total blocked shots (number of teams, and average number per year) GPG - avg number of power plays, PP %
1997-98 - 17,564 (26 teams, 676 each) 5.28 GPG - 380 PP/15,08%
1998-99 - 23,813 (27 teams, 882 each) 5.27 - 359 PP/15,81%
1999-00 - 26,165 (28 teams, 934 each) 5,49 - 331 PP/16.15%
2000-01 - 28,735 (30 teams, 958 each), 23.36 - 5.51 GPG - 376 PP/16.64
2001-02 - 28,653 (955 each), 23.30 - 5.24 GPG - 338 PP/15.47%
2002-03 -
2003-04 - 28,293 (943), 23,00 - 5.14 GPG - 348 PP/16.46%
2005-06 - 31,959 (1,065), 25.98 - 6.17 GPG - 480 PP/17,68%
2006-07 - 33,182 (1,106), 26.98 - 5,89 GPG - 398 PP/17.58%
2007-08 - 29,660 (989), 24.11 - 5.57 GPG - 351 PP/17.75%
2008-09 - 32,324 (1,077), 26.28 - 5,83 GPG - 341 PP/18,95%
2009-10 - 33,452 (1,115), 27.20 - 5.68 GPG - 304 PP/18,23%
2010-11 - 34,904 (1,163), 28.38 - 5.59 GPG - 291 PP/18,02%
2011-12 - 29,208 (through 1,032 games; 974 per team, 28,30 per game) - 5.45 GPG - 228 PP/17.45%
This year, 27/31 teams have over 1,000 blocked shots and the other 4 are all over 900. In a single game, we're likely to see over 30 blocked shots between the two teams. The average for the year will likely end up over 1,200 per team, and the number of blocked shots is roughly 20% higher than the number of missed shots.
Watch a game from 20 years ago, or 25, or 30, or earlier, and then tell me that "it's always been part of the game". It hasn't been.