Lillard and McCollum are hardened veterans and they are who they are. They aren't suddenly changing their style of play or shot selection because a new coach "holds them accountable," whatever that means. This simplistic notion that Stotts said, "Good job, guys, take bad shots, I love it!" while Billups will come in and tell them, "Hey, bad shots are bad, take good shots" and things will change thanks to that accountability was never realistic. What people probably didn't understand about the concept of Stotts being a "players' coach" is that he very likely built the offense around what his best players actually do well and gave Lillard, especially, input into it. This was a Stotts-Lillard combined creation and most teams want a head coach who can do that--connect with their franchise player and build an offense together that actually fits that franchise player. Billups will only be successful if he can also build an offense that actually fits what Lillard does well and what Lillard believes makes use of his skillset. It's possible but unlikely that that offense will be diametrically different to Stotts' offense, especially when you consider that it also has to fit all the other existing players. If Billups is a truly innovative offensive coach, it's possible he can pull that off--but since those coaches are very rare, the odds are against it. So the overwhelming likelihood, IMO, is that when the offense eventually stabilizes, it'll look a lot like the one the Blazers ran under Stotts.
I don't think Stotts was an innovative coach, just a competent coach (of offense) that knew how to maximize his best players. Since the roster has largely not been filled with much talent beyond Lillard, that offense isn't going to have a whole lot of success against teams that can, in the playoffs, spend a series game-planning to limit Lillard. So it's a successful regular season offense that sputters in the playoffs. Even a great offensive coach might be able to trick his way past a team or two, but would be exposed by a strong playoff defense when you only have Lillard, a flawed secondary player like McCollum and very little else.
Does it matter to me that Stotts is gone? Nope. But I think a lot of fans were fooled by Olshey's misdirection, focusing on the factor that can't change things substantially (the coach) and ignoring the factor that has to change in order for Portland to be a contender (the roster, which means Olshey would be the fall guy--no wonder he didn't want fans paying attention to the actual talent on hand).
It wouldn't surprise me at all if Billups is a superior coach to Stotts. But I sincerely doubt it'll be obvious, as Billups struggles with the same impossible roster math that Stotts did.