Its not so much they built the Garden for the 'rich' as much as the corporations that can write off the cost of the suites. To me what really sucks about the place is that after the lower bowl loge seats, the next really good levels are occupied by suites. The balcony seats in my opinion are too high.
At the same time, the place really has decent acoustics as it gets loud for big games. If I could change one thing about the place I'd try to figure out a way to the real fans closer to the action but I also get the economics.
A Celtics only arena wouldn't work though it was explored at one time, I believe during the Gaston era. They looked at land off Route 1 in Revere and I believe at Suffolk Downs prior to all this casino stuff. The big problem is the Garden's in the prime location both in terms of highway access as well as commuter rail and subway.
And with that area really being built up right now, that will remain the place to be moving forward.