I think Smart was seen as a higher quality prospect than Jaylen Brown is. Like if you check out Chad Ford's yearly "Draft Tier" article, apparently according to scouts/experts Marcus Smart was a "Tier-2" level prospect... meaning a player with all-star potential. Brown is seen as anywhere from Tier-3 (starter potential) or Tier-4 (rotation player potential).
Despite this, guys can always disappoint or exceed expectations. In the case of Smart, he been a major disappointment thus far and hasn't at all lived up to what he was billed as. For two years, he's been nothing more than a defensive role player and offensive albatross. Hopefully Brown goes in the other direction and vastly surpasses what people think he'll be. The fact that he's 19 and shows some raw ability has me really excited to watch him develop. I'm looking forward to seeing what he turns into long-term. I have no expectations in year 1. He's really raw and looks like he's a long way away from contributing.
Projections are crude, but I like em. Although Brown is Tier 3, I wonder if the strength of that Tier 3 class may have impacted his perceived upside.
The idea behind Ford's article isn't to compare players within a class... it's to compare them to every prospect that's ever come out. Obviously, some players will exceed expectations (like Rudy Gobert) and others will disappoint (like Marcus Smart), but it's interesting to see how players and draft classes are perceived. In 2013, there wasn't a single player listed as a "tier 1" or "Tier 2" prospect. This was reflected in guys like Anthony Bennett, Otto Porter, Cody Zeller and Alex Len going in the top 5. Not all "Top 5 picks" are created equally. Nobody would confuse Anthony Bennett or Cody Zeller with a "Tier 1" prospect like Anthony Davis or Karl Towns. None of the guys taken Top 5 in 2013 were thought to have superstar or even allstar potential. Jaylen Brown is similar to those level of prospects.
That doesn't mean it would have been unthinkable for Anthony Bennett to develop into a star. And it's not unthinkable that Jaylen Brown will develop into a star. Raw prospects like that are exciting. It's fun to see if they put it together.
Ford's "Tier article" makes sense to anyone who understands that yearly article. It's not like every single draft class has X amount of future superstars, X amount of future allstars, X amount of future starters. It varies from year to year. Ford just relays what Scouts/front offices tell him in regards to players in a draft class look. Guys like clay can scoff at it, but it's helpful to a certain extent. The consensus from professional scouts apparently is that Brown falls somewhere in the Tier 3/Tier 4 range (future start/rotation player). Smart was projected to be a future star. IF we are comparing Smart to Brown as prospects when they both entered the draft, Smart was seen as the superior prospect. That doesn't mean Smart will be a better player. Some people have a really hard time wrapping their mind around that concept.