It's not problematic to reference Apache 2.0, it's a fine license. I assume what berkay is talking about is this wording of "<existing license> with Commons Clause" - e.g. the Apache foundation has explicitly requested that this not be done (which the creators of the Commons Clause conveniently ignore), because it changes what the license means a lot and sounds like it's an official variant of the license. Apache only wants if any "Apache 2.0 with addons" licenses if they give more rights to the recipient, not less.
I remember that I read some things about mixing Apache 2.0 with other restrictions (like Commons Clause in this context) and a lot of debates about the wording of such mix.
I am curios as I read some resources about various OSS licenses and after I was thinking that Apache 2.0 license is a good one.