Yes that is true that game at first sight is playable for everyone. There is nothing fancy there on interface level and it is not a problem to follow some basic mechanics (btw I have written first version of this game when I was 15 years old on Commodore 64).
Still when you play it there are some concepts which is hard to understand for younger persons.
- For learning economics it is bit tricky of course it works on long term but now players wants immediately reward, as there is some randomness in the game (based on the principle "Art is not the math") some players have problem with this.
- Also problem is to understand the currency in the game are not USD but some abstract currency which is not comparable with anything in the world (especially with salaries or profits real movies which are currently in BoxOffice).
- Another concept is abstraction for example limited number of cast "Why I can't hire unlimited number of actors like in Avengers".
- Or why you can cast sport star or political in the movie? (it looks that more choices is problem for some players)
- game can be taken a bit more seriously or less seriously (and some players have problem with party "why so serious" ;)
About knowing the movie it partially true as it is not mandatory but it gives some additional context and layers of fun (with cult characters concept or cult movies which based on IMDB real films)
So there are small things which requires some abstract thinking and younger audience have problem with it.
So to make it summary yes as you write this is for mature players in not common sense (as most of the ratings based on content) but still I would like to suggest some age category for players. As you do not watch Tarkowsky's or Bergman's movies with 7 yo kid.
P.S. I won't comment your movies preferences as everybody has it's own taste and perception of specific movies :)