To be pedantic, I don't think the Diffie-Hellman is the weak link as it doesn't specify the group or generator. It just requires that given g^a and g^b it's hard to determine g^ab. And obviously if your generator is poor the preconditions to the algorithm don't work. And then as what the post-conditions for what DHKE provides. It just establishes a shared secret with the person on the other end of a connection. You have no idea who that other person is, but you can communicate securely with them (which is why you need authenticated encryption).

I guess a better wording would be "It's extremely easy to implement textbook Diffie-Hellman Key Exchange in was that don't satisfy the preconditions of Diffie-Hellman, and this are gravely insecure."