Ultimately I think it has more to do with talent then system. Even if the Sixers could go far with a defensively triggered small running team (Like the Showtime Lakers when Worthy played some PF), the team needs more stars to be a contender. I guess Speights and Thad could become stars, and Iguodala has all but arrived as a secondary star.... Brand was supposed to add the higher level star to the mix, but I'm not so sure anymore.
We will know much better next year, the shoulder should be fine and he will be the two full years out from the achilles that other athletes ahve said you really need. On the other hand he will be a year older.
While I agree that the Sixers play better pressure D than the current Suns, Knicks and Warriors teams, they have problems against teams that protect the ball well and slow things down (think Detroit and Utah), plus as tk said, there is an overall prime talent gap between them and the elite teams at this point. I think the sixers talent level is very high, but much of it is not ready for prime time talent this year. One thing I like about the sixers young talent is that most of these guys have good heads on thier shoulders in addition to tons of ability. The future of the PG spot still bewliders me however.