Actually, Jacksonville is #14 in average home attendance. Arizona, Oakland, Indianapolis, Chicago and San Diego are all leading the league in lowest average attendance. The #1 teams are Washington, NY Giants, KC and NY Jets. The league average is around 62K, whereas Jax is around ~70K.
The numbers don't back up this argument.
NFL Football League Attendance
Team Home Avg
WASHINGTON 87,834
NY GIANTS 78,734
KANSAS 77,921
NY JETS 77,898
CLEVELAND 73,105
MIAMI 72,601
CAROLINA 72,071
DENVER 71,961
BUFFALO 71,800
HOUSTON 70,649
ATLANTA 70,596
GREEN 70,550
BALTIMORE 69,824
JACKSONVILLE 69,433
TENNESSEE 68,917
NEW ENGLAND 68,756
PHILADELPHIA 67,609
SEATTLE 66,680
ST LOUIS 65,923
CINCINNATI 65,531
TAMPA BAY 65,340
SAN FRANCISCO 64,784
NEW ORLEANS 64,147
MINNESOTA 64,121
DALLAS 63,862
PITTSBURGH 63,423
DETROIT 62,395
SAN DIEGO 60,683
CHICAGO 58,907
INDIANAPOLIS 57,099
OAKLAND 50,090
ARIZONA 37,533