All movies take place in fictional universes.
No they don't.
Yes they do. Fictional films are a creative work; the result of writers, screenwriters, directors, actors, etc. These give rise to a work of fiction: including the universe in which its set.
To elaborate: Saving Private Ryan allegedly took place in WW2. But unless you really think that Tom Hanks was storming the beaches of Normandy, you have to accept it is a fictional depiction. Gladitor allegedly took place in ancient Rome. But agian, unless you really think Russel Crowe and Joaquin Phoenix duked it out in a colosseum, again fictional.
The funny thing is we seem to willing to accept that actors are playing fictional roles; we can largely suspend disbelief for them. But we seem unwilling to similarily suspend disbelief for the setting; which is, even if based on our reality, ultimately fiction.
Personally I've found the moment I accepted that all ficitonal films take place in fictional universes, yes, including films "based on true stories", history, etc, it makes them much more enjoyable. Suddenly nitpicking things like how C Company of the 2nd Rangers didn't actually land in Dog Green Sector or how roman emperors didn't actually duke it out with slaves become irrelevant. It's just how things worked in those fictional universes.