I think its massive risk/reward. Its not even his current play, its his high potential to be a negative cultural impact on a young team.According to a lot of advanced stats he's still a positive impact player.
If you think about it that Simmons is only an additional year past KO/Conley, you can say your paying 40 million for a far reaching 1st rounder that will have exponential value to the Mavs in a scenario where you try to get Luka after Kyrie blows up in their face.
I wouldnt write it off before a thought but but i'd lean heavily to a "no" right now.