Yes, the story is fictional - but it still is a great story and a great movie. The only movie I saw five times during its original release. I had little appreciation for opera (or choral music at all, other than Beethoven’s 9th), but seeing the snippets staged for the movie changed that (along with the excerpts from the Requiem at the end).
I’m not sure I’d call Mozart a “free thinker”. What he was, was an extremely immature and crude individual who, like many of today’s child stars, went off the rails with wine and women and being extremely rude to his employers (who were largely very important and powerful people) but *mostly *got away with it because he was a musical genius.
Note that Mozart was not, by and large, an musical innovator as such - a lot of the elements of what he did could be seen in the works of other composers (particularly Josef Haydn and Johann Christian Bach). What he did do - and let’s not understate his amazing level of skill here - was to do it far better than anyone else, and to synthesize the existing musical idioms into a new and better form (see for example the aforementioned “Magic Flute”, in which the vulgar Singspiel form suddenly becomes something transcendent).
Beethoven was an innovator. Mozart was a synthesizer. Both were geniuses.