The term "dated"

" showing the facts or style of the past rather than of the present"

People always say something's dated as if it's a negative thing. I personally love it when a production shows its age.

Very true. It's particularly odd to criticise a film for looking and sounding like it was made in the 70s, 80s etc when you have many modern movies trying their best to recreate those times today.
I suspect that, like "cheesy" and "progress", it's one of those words that means whatever the person uses it wants it to mean.
Like the moron crowd who'll describe 80s action movies as "cheesy", and then head off to the cinema to catch the latest Marvel movie. Um, okay dude...

It seems like people think something looks 'dated' when it was made 15/20 years ago, but once it gets to 25/30 years ago, it changes to 'classic'.