(SGA) came in a trade not from their hoard of top draft picks.
Boston's drafted top players are not the elite players in the league either. Tatum is great, but he's not an MVP candidate. I'd argue that Brown is not even Boston's 2nd most valuable player. He's their 2nd leading scorer but definitely not close to their most efficient scorer. Boston wins a lot of games because they're probably the deepest team in the league. They can survive injuries.
Again, with the new lottery rules, NO team is guaranteed a top draft pick so talent evaluation and player development is much more important.