I think because Kupp isn't a me-me guy that demands attention, his accomplishments go a bit under the radar.
No doubt all the coaches are aware of him. But I loved hearing "kuuuuuuuup" from the stands in Arizona.

He's a class act that doesn't beat his chest and make gestures towards the sky for doing his job. Makes a great catch or gets a TD and he just hands the ball to the ref and walks away.

He's the best WR in the game right now. Period. Stafford's lucky to have him.