Kirk isn't the problem. He really isn't. There are a number of things holding him back. The scheme is trash. His route tree is limited to mostly go/post, curls at the sticks or passes in the flat for screens or off motion. Like Nuk he's kept predominantly in one position so they don't move him about to help match ups.
Combine this with Kyler struggling to read defenses and missing several opportunities to Kirk where he should be the first read, or just missing he's open.
I have no idea whether Kirk could produce much more or not because he's playing in handcuffs in this system.