I bet if you add up our production at each position we are top of the league. We also don't suffer the same drop off teams do because we have depth and don't have many players playing a ton of minutes.
PG-Isaiah
SG-Bradley/Smart
SF-Crowder/Turner
PF-Sully/KO
I bet if you add up all these positions we are close to top of the league. Center is really the only position we are average and Amir is serviceable and a good glue guy. It makes sense why Ainge would target a young center to go with our group though when you look at it this way. I'm tired of media speculation though in general. The media just runs with stuff that isn't reality.
Sully and KO are a very good PF duo. We are strong at guard. We have an allstar in Isaiah. Crowder and Turner and who we mix in is also strong.
KO is out, suddenly Sully's minutes jump. Whether he can play major minutes like that over long stretches is something else but as far as a duo they are very good. We have depth behind him too.
On paper, I agree that our combinations of guys at most positions can probably compete (production wise) with other team's singlar star players.
For example, I believe that the combined production of Sully and Olynyk would be greater than the production of Horford or Olynyk on their own.
BUT
The key thing is that you can only have one of those guys on the court at a time, and that means that no matter which of those guys is in the court, you're always sacrificing something.
When Sully is on the court we gain rebounding and post defense, but we lose outside shooting, dribble penetration and the ability to defend quicker bigs.
When Kelly gets in the game we gain outside shooting and dribble penetration, but we lose rebounding and we lost posts defense.
If you have an Al Horford in the game, then you have rebounding, you have post defense, you have outside shooting, and you have the ability do defend quicker bigs - all at the same time. This means that at any one time, you have less holes/weaknesses in your game.
Likewise Love would give you Olynyk's outside shooting and dribble penetration, but without sacrificing Sully's rebounding.
That is the core difference between having a good starter (like Sully or Olynyk) versus a borderline star (like Horford or Love).
How much you gain from that I think depends on the circumstances, and also on the versatility of the rest of your roster.
Having Olyny sacrifices rebounding and low post scoring/defense, but if you can combine him with a big who can do those things (e.g. Dwight) then it's a moot point.
Having Sully sacrifices the ability to defend quicker bigs and the ability to stretch the floor, but if you have a big out there with him who can do those things (e.g. Thaddeous Young) then that becomes mostly a moot point.
You can be just as deadly a team without those star players IMHO, but it means you need to be far more careful of how you piece your rotations together.
Once you get up into the realm of real superstars (like Anthony Davis, Karl Towns, Demarcus Cousins, etc) then it changes everything because those guys are so versatile and so incredibly skilled that the one star player on his own is good enough to do what an opponent's entire frontcourt can do...so you can pretty much add ANYBODY alongside that player and you will dominant their end of the court.
So are star players overrated? Maybe, but superstar players certainly are not.