How to nicely inform a designer that he is not worth the money he is getting and to stop bragging about it?

Not ;) I think

Hahahaha same thing here

It's simple: "hey dude what is the difference between now you and in five minutes futur you? Both don't have a job anymore"

How about using someone else and saying something like "Yeah dude, we know your work, and it is great, but for this project we wanted to try out a new perspective, be a little experimental 😀👍" - when he requires why he wasn't asked. Could only either cause a tantrum or instill a little bit of self reflection.

"nice, so where's the actual design?"

@xalez haha, you used the word nice, best answer so far

I don't think there is a nice way to let someone down.

But if what you say is true then what they are doing isn't nice either so touche.