Think about it. Most of these 20 something stars know a lot more about the Celtics 20 years of mediocrity then they do of their 4 years of success. For the majority of their lives the Celtics have been bad. They don't see the Celtics as an established winner over the long haul.
Why would the record of the Celtics in the 90s matter, though? If the argument is that players are not looking historically, why would they look past the last 6 or so years? I mean, there are two ways to look at a franchise. An inclusive one that takes into account its entire history, or one that only takes into account its current incarnation. Pre-Doc Rivers/Danny Ainge era Celtics are a different thing entirely from what they are now. We have been a consistent contender for several years.
Basically, you can't have it both ways. The mid 90s are a long time ago, especially for 20 somethings. I barely remember them, and I am the same age as most of these guys. Either they care about the history, in which case the legendary Celtics teams of yore overshadow the mid 90s anyway, or they only care about recent history and the future.
EDIT: Hell, 2006-2007 was terrible for Boston, and 2004-2005 was terrible for L.A., and 2007-2008 was terrible for Miami, etc. etc. Every franchise has terrible stretches, many of them in recent memory. Unless they are terrible right now, or are about to GET terrible, who cares?