From what I've heard there are two things. First, which seems almost universally accepted is that the 2016 class isn't as deep as the previous two. Second, in comparison to 2014 and 2015 the top talent isn't view as favorably. Experts I've read thing the Wiggins, Parker, Embiid and Towns, Russell, Okafor groups have more star potential than Simmons, Labissierre, and Brown crop. An observation I've made about the 2016 class is that the kids do look to be a little older age-wise than previous classes too.
I for one though, am not ready to write the 2016 crop off yet. I think Simmons might be a bit of a victim of over exposure. He's been a top NBA prospect for 3 years now and I think he's being picked apart like college guys who return for their senior year. Also, Brandon Ingram seems to be flying up the board. He is growing like a weed and is young for his class. Finally, I think Jamal Murray will become a top 10 pick by draft time next year. He's talented and underrated in my book.
That said, 2017 looks to be stacked. Harry Giles, Josh Jackson and Jayson Tatum look like future all NBA guys.