A real UX person will be able to and should provide high-fidelity mocks of the entire flow, preferably with an interactive demo of some kind. They will certainly have design skills and preferably programming skills. However, those high-fidelity mocks are the last stage in the UX design process. If all you want are those final mocks then you are doing nothing more than asking for a new coat of paint, and what you really want is a graphic designer.
So, you're right, everyone on the team should be responsible for good UX, but it really helps to have someone who can slam together some mocks after the meetings, or whose job it is to come up with a completely new idea to solve our nasty onboarding flow problem. Because George, the guy who's in charge of making sure our DB doesn't implode under load? He might be able to help out with the UX, but he's already got a full-time job to do.
Your image of a UX person that produces no mocks, no prototypes, no designs, and just sits in meetings is a sad one. Those people should be fired, because they are not doing anything -- certainly not UX.