Is the movie about freedom?

No it's not. It's an indictment against life-stifling legalism in general and, specifically, that of American mental institutions in the mid-50s (Kesey wrote the book in the late 50s). The novel wasn't inspired by Christian legalism, but rather by Kesey's time working the late night shift as an orderly at a mental hospital in Menlo Park, California, where he got to know the patients and witnessed the inner-workings of the asylum. Kesey did not believe these men were lunatics, but rather that they simply did not fit society's box & the "rules" thereof; as such, they were exiled to the institution as rejects, which didn't help them, to say the least.

Of course, the ideas in the movie relate to any institution where legalism might infect the people, not just mental hospitals, e.g. family, school, job, military, church, ministry.

"Footloose" (1984) is another great anti-legalism movie.

You obviously have never read the book.

You equate false analogies with thinking?

Given his own background (fleeing from Czechoslovakia, and all that), I think Milos Forman probably read the story that way, at least in part: the flawed individual against the repressive regime with the repressive regime ultimately destroying said individual.

But I think you could read it multiple ways. Which is why I think it endures.

It's an allegory about any authoritarian system that oppresses, controls, and crushes those under its powerful thumb. And authoritarian systems can run the gamut from far right to far left, religious or secular. As O'Brien says in 1984, power exists for the sole purpose of perpetuating itself. It can profess all the good intentions in the world, and its adherents can often even consciously believe that what they're doing is for some greater good—but in the end, it's all about power over others.

That reminds me to the Hitchhiker’s Guide to the Galaxy and "The Outside of the Asylum"...