That is exactly right. Monk wasn't even considered among the best WRs when he played, only being named to the Pro-Bowl 3 times in his 16 years in the league. He only has 5 1000+ yard seasons to his credit, and only 6 when he caught more than 70 passes. Compare that with Irvin who had 7 seasons of each in his 12 years. Had Irvin not gotten hurt he would have accumulated better numbers.
Monk played in 65 more games than Irvin and has almost 200 more receptions, yet he has only 3 more TDs than Mike. He was not a big play guy. In fact the best comparison for Monk is Keyshawn Johnson, another guy who makes the tough catches, gets 1st downs, collects a lot of numbers, but isn't a big play guy.
All that said, I do think Monk belongs in the HoF but he's got a lot of guys ahead of him (Bob Hayes for instance).