It's just so hard to hit on a draft pick no matter where you are but even more so late. Yeah, they got Maxey very late-round and Bridges was a 10 but then so many of the Sixers' other super-high picks all mostly flopped (besides Joel). They can rebuild around or without Maxey but they are all-in for the next 2-3 years. If Joel suffers a huge injury during that time then they can hope for a tank-like year (though they still might not horrible enough), or actually tank.
That's also why older players aren't really a huge concern other than the fact that they, too, could be injured. But the shelf life doesn't have to be long.
