Art Monk was only a 3 time Pro bowler an only one time an All-Pro. Yes his 100+ catch season was awesome--his all pro year. But he never got near it again. He played 16 years and he broke 80 receptions 3 times. He never got to 10 TDs scored in any one year.
The truth is he had one Hall of fame caliber season and other than that he just lasted a long time. He ranked top 10 in receptions 4 times and top 10 in receiving yards only 3 times. He only ranked top 10 in receiving TDs one time and that was 9th.
He was a good, good player but he basically had 1 season where he was an elite Wr and 2 more where he was a top 10 WR. That just doesn't add up to Hall of Fame.
http://www.pro-football-reference.com/players/M/MonkAr00.htm?redir
Gary Clark made more Pro Bowls and Charlie Brown made 2 Pro Bowls. Often surpassing Monk on the same team.