For many people, your assessment is probably spot on. I would like to suggest a little nuance that may apply to another group.
It's not actually about authenticity. It's about spirit and ease. This is difficult for me to describe, so if it doesn't register, I apologize in advance, but here it goes:
The idea of Old Hollywood at DHS (or MGM) was something that couldn't actually be visited. Not only because it was themed to a past many decades ago, but also because it never actually existed as depicted. In that way, guests got to enjoy the spirit of Hollywood, not an authentic recreation. Authenticity requires all sorts of things that most of us would rather not worry about on vacation. For example, no trip to a major city is complete without panhandlers, a slightly greater possibility of pick-pocketing or petty crime, pollution, traffic, etc.
Specifically when it comes to World Showcase, the goal is not to replace a trip to the actual country. It is about getting a taste without the travel, language barrier, currency exchange, visas and all the other minor annoyances that would add up quickly if you were to try to take a trip that visited that many countries. In some ways it's like a travel brochure, you get to see some architecture, cuisine, etc. without getting the full experience. So it is authentic, but only in so far as it is acknowledged to be a "sanitized" experience with limited scope.
I suppose what it boils down to for this group is that they enjoy the "Disney" version of real places. In some ways I guess it could be viewed as similar to a zoo. You get to see animals, but it's nothing like animals would be in the "real world". They aren't eating each other, threatening you for approaching them, separated by thousands of miles and different climates or any of the other real world "problems" with visiting wildlife.
It's not necessarily that people prefer World Showcase over the real thing (although some definitely do), it's more that it is a practical taste of the real thing that focuses solely on the positives.
If we apply the zoo analogy to theme parks, I would imagine it would be something like this:
Pure Fantasy (ex: Fantasyland) -> Awesome movie about animals that can talk
Highly Themed (ex: EPCOT Center) -> Visit to a well-done zoo
Real Thing (ex: I suppose Adventures by Disney?) -> African Safari
Each of those categories would apply to different people for different reasons.
I don't know if that made any sense at all, but I tried, haha.