Webber had 6 seasons of at least 20 points, 10 rebounds, and 4 assists. 3 more of at least 20, 9 and 3.4. A bunch of other really good statistical seasons. All of this while being fairly consistently injured. He took a number of pretty sub par teams to the playoffs. He is basically Kevin Garnett without the trade to Boston or a better version of Chris Bosh without Miami.
He is also a better player than a number of players in the HOF and there aren't that many that are eligible that aren't in that are better than him (I can't actually think of one). I think he probably gets in someday, but not on the first ballot, especially if his time at Michigan is counted.