It's objectively not worthless. You get a breakfast credit, you earn more points on your spend, and you'll typically get an upgrade to at least a higher room category if there's one available.

You're probably not getting upgraded to a suite (though it can happen) and no, the front desk typically won't bow and scrape for you.

I don't stay in many Hiltons (they generally have less appealing properties, with less at the high end than either Hyatt or Marriott) but as long as you keep expectations in check it is definitely better to have Diamond when staying at a Hilton than not.