If the Choral Fantasy is "cliche-addled," what is "Magic Flute?" Mozart himself admitted he was embarrassed by its mediocrity. Besides the Jupiter, name another symphony of Mozart's that compares to Beethoven's Fifth, the Eroica, or even the Pastorale? And then there are the incomparable Beethoven piano works, his superlative Violin Concerto, and pieces like the Egmont Overture, Consecration of the House, and the Seventh.
Mozart wrote plenty of flawed -- and forgettable -- music. He was barely in the same league as Beethoven, and certainly nowhere near his master. Because Beethoven had none.
Ask a musician about Beethoven’s choral writing in the 9th symphony and elsewhere. He had no feel for the human voice. None. His one opera Fidelio has great moments but is not vocally adroit. The Choral Fantasy is a minor work that is virtually never performed. ‘The Magic Flute’ pops up on lists of the greatest operas ever written. Mozart actually revolutionized opera and the concerto. He pretty much invented the piano concerto as it came to be understood. There were no stand alone overtures or programmatic orchestral pieces in Mozart’s time so it’s useless to look for a corollary to stuff like the Egmont and the Consecration of the House. Mozart also gave up writing violin concertii in his teens.
You seem to be putting eras up against each other as opposed to composers. In the 18th century the qualities looked for in music were balance, clarity of line and emotional restraint. Those are the qualities Mozart exhibits. He was also the most radical composer of the 18th century...harmonically much more advanced than Haydn. He’s a utopian composer. His music has an otherworldly beauty that Beethoven hinted at occasionally.