I'm going by terms used at vintage fashion fairs & vintage shops that I visit.
Most of them (including a couple that I've been going to since I was a student 35 or so years ago!) do now stock pieces from the 80s/90s/2000s, though are selective in what they'll choose to sell.
The terminology does matter depending on what age you are, in that to someone who's 25, & didn't wear 90s slip dresses first time around like I did (as they weren't born!!), everything that was made 20 years ago or more is vintage - they don't/won't/can't differentiate?
And retro has a different meaning - it means something new that is mimicking something old. So, yes, that dress WAS retro in the 90s when it was made - but it's now 2026 & it's become vintage ...
Rehashing ideas & styles from past eras is nothing new & will continue as long as there's a fashion industry. 1970s styles (which I assume you would consider "true vintage"?) aped lots of 30s & 40s clothing, but also harked back to all the lacy romantic Edwardian/Victorian eras. So some of it was also retro at the time.
What my goddaughter considers to be the vintage clothing of today will eventually become "true vintage" to her as she gets older, & she'll scorn the clothing of the 2020s being called vintage - just as @GarlicSomething has pointed out regarding the vintage clothes of her youth! (And mine!)