I believe Simmons has the makings of a two way player, able to impact both aspects of the floor, offensively and defensively.
Obviously initially, due to lack of experience he had defensive mistakes, but he was able to make an immediate impact offensively. So I would not label him an offensive player, but initially regardless of his defense, he had an offensive impact right away, and will only get better.
Kyle, on the other hand, doesn't have much of an impact offensively therefore you need to be strict with him defensively.
Everyone needs to have a role to get playing time. It's ironic, because defense was not Kyle's strong suit ever, but he's improved. Basically, despite it not necessarily being a srtength of his, his playing time depends on how good he is defensively. If he's good defensively he will get playing time that will allow him to be better and improve in all other areas.
He will get chances in the future, but you could say their roles have reversed. Kyle will now play when there are injuries, foul trouble, Manu is resting, or someone is really, really laying out an egg, or if there is a matchup problem that J.Simms can't handle. If he keeps working hard he will make the most of his chances.