I pulled the top 20 stats and I beg to differ the difference is as vast as you proclaim. The season passing yards are 3228.2 for 1986 versus 3976.8 for 2013 a difference of 748.6 yards. Take into account the QBs were less protected and took more hits, and the main difference can be attributed to the average QB in 1986 playing 14.7 games vs 15.6 games in 2013. Also the Games Started is 14.1 to 15.5. Getting to play an extra 1.5 games can further explain this statiscal difference.
Have yards gone up? Marginally. Has the game changed? No. Clearly the numbers show the difference is much less than some on TBD would like to admit. This is not like comparing 1986 to 1959. The modern vertical NFL pass offense came about in the mid to late 1970s and guys like Dan Fouts really revolutionized the game.
Top 20 QBs 1986
Games 14.7, Games Started 14.1, 254.4 completions, 447.0 attempts, 56.9% completion %, 3,228.2 yards, 18.3 tds, 16.6 ints, sacked 33.4 times, 254.9 yards
Top 20 QBs 2013
Games 15.6, Games Started 15.5, 347.8 completions, 558.3 attempts, 62.3% completion %, 3,976.8 yards, 25.7 tds, 14.9 ints, sacked 37.9 times, 259.2 yards