Yeah, I don't think that is the issue with him. Everyone knows he knows how to play basketball well.
Here are the issues.
1. His teammates do not speak positively about him. Some have actually publicly stated something is off when he is in the lineup and they play better without him.
2. Supporting this statement - look at their record. If he is really a top 20 nba player, and so is Beal - why is that team so bad?
3. His contract. He is guaranteed 37, 41,43, and 47 million per year for the next 4 years. The entire Salary cap is around 100 million right now. meaning he alone eats up a third of it - add in bookers contract which is less - but still nearly another third and two players take up nearly 2/3 of the Suns cap space. This means no free agents other than ones signing for the minimum for the next 4 years - and probably longer since Ayton and Bridges extensions will kick in as soon as walls contract ends.
So getting Wall means essentially other than draft picks you are looking at the Suns team for the next 4 years. Considering their complete ineptitude as of late - do you think John Wall along with our current set of players is the roster you want for the foreseeable future?
My answer is definite - NO. Only a top 5 player deserves a supermax contract, and wall is not even close to that.