Going into the season, it looked like Portland would have a strong bench with Jerrod Bayless, Wesley Matthews, Marcus Camby, and Rudy Fernandez. They traded Bayless and Camby was thrust into the starting lineup by another Oden injury.
I can see how some people would like the Bucks bench better the the Celtics. The Rockets have a deep bench that they rely on more than the Celtics. Just because the Mano Ginobelli is starting now, that doesn't mean the Spurs have a crap bench.
The main flaw of the Celtics bench is lack of scoring. If you treat Shaq as a starter, Boston has only one player (Nate Robinson) scoring more than 14 points per 36 minutes. Many teams have 3-4 players on their bench scoring at that rate. I don't look at Robinson, Davis, or Daniels and think that any of them should be starting on many NBA teams.
Given a lack of a near All-Star level player who could start but is coming off the bench and a lack of offense, the Celtics bench is going to be undervalued by people. I don't see anything wrong with someone saying Boston doesn't have a top five bench. I also think it is not so far-fetched for someone to honestly believe that the Celtics bench isn't top ten.