The defense that the characters were meant to be iconic stand-ins is also undermined by the inclusion of so much accurate trivia (in addition to the many inaccuracies)
The real Mozart on the other hand, as we know him from his letters, did have a penchant for the vulgar, for the irreverent, for scatalogical humor, for good booze, for pretty ladies, and all the rest of it. Of course that's just one side of him.
Young musicians aren't so incredibly stupid as to be "harmed" by Amadeus – it's clearly entertainment. One of its messages is that you can dedicate yourself absolutely to the development of your art while retaining a sense of playfulness. Another message is simply that this music is incredibly rich and exciting and profound, music you can explore for a lifetime.
So in order to be watchable, the movies instead focus on the artists personality and private life, and the actual work part is reduced to the cliche of a flash-of-inspiration followed by a short montage of frenzied all-night work, resulting in finished masterpiece. This is of course an unrealistic depiction of the artistic process.
The movie Amadeus makes a point out of how effortless Mozart creates as opposed to Salieri who has to struggle and only gets mediocre results. This is really the romantic myth of the inspired genius, and by playing up the silliness of Mozart, the movie shows genius as a divine gift wholly separate from the persons daily life. Showing Mozart practicing, struggle, making false starts, iteratively improving, having to scrap work etc. would undermine the message of the movie. This is the absolute opposite of the modern 10K hours myth which states that anyone can be a genius through hard work and dedication.