Why would you expect Ingram of all guys to bust? He has the complete skill package. It's not as though he has to add new things to his game or improve drastically in any area to become great. He's the most likely player in the draft to become an above average starter.
I strongly disagree with all of the above.
Honestly, Ingram does not have a single elite skill. The biggest reasons why he's ranked so high is because of:
a) His age
b) His size/length at the wing position
He's a very good shooter which is probably his most impressive talent, but:
1) He's not an elite athletic (above average, but not elite)
2) He's not as good a ball handler / passer as advertised
3) He's now a standout defensive player (though potential is there)
4) He's a solid but not great rebounder
5) He's not en elite scorer right now, but has the potential to become one
6) There's serious question marks about whether he's got a star's mentality
These are all very valid question marks even BEFORE you get to the concerns over his physical build.
Ingram is a far riskier prospect then people are acknowledging. The upside is certainly there, but so is the risk of him bombing out.
Simmons has far less risk of being a bust since we already know he's going to rebound at an NBA level, we know he's going to be able to use his size and explosiveness to score in the P&R, and we know he'd going to be able to score in transition. Simmons' has an almost Lebron-like combination of speed and strength, so on the fast break he's going to be like a freight train - he'll be next to unstoppable. He's going to be able to muscle his way against small forwards, and he's going to be able to blow past PF's and C's with his ball handling and quickness.
At the very least, Simmons will be a 14/10 guy at a bare minimum. If/when he develops a passable jumper and a quality better post game, he'll be completely unstoppable. If that never happens, he'll still be a comfortable 14/10 guy at a minimum.
Really, the only defense plan that can be used against Simmons will be to sag off him and let him shoot. There's really nothing else you can do. If he develops even just a passable jumper, there will be little to no answer against him.