> He divided Beethoven’s music into an early style, imitative of Haydn and Mozart; a middle style, grand and exhortatory like the Eroica Symphony; and a late style, more private than public, that meditates on eternal questions of form.
A few things about this filter through which Beethoven is often heard:
Early on, Beethoven mastered and began to extend a particular technique of Haydn's: motivic development. There were a lot of aspects of Haydn's music which he didn't imitate, like Haydn's proclivity for witty musical jokes.
In the early pieces where Beethoven imitated Mozart, the imitations aren't anywhere near the level of sophistication of any of Mozart's music that Beethoven would have been studying. Young Beethoven in no way mastered Mozart's lyrical writing, breadth of musical allusions, contrapuntal control, formal complexity, or (especially) operatic textures and virtuosic arias. He certainly tried to emulate Mozart by attempting to write the highest quality music he could, but by any serious measure he failed to achieve this in his early period works.
At least to my ear, the beginning of Beethoven's Piano Sonata, Op. 101 is the first piece that attempts to "imitate" Mozart melodically while actually approaching the level of overall sophistication of what are considered Mozart's greatest melodies. But this is the beginning of the "late period," which is supposed to be the master composer looking inward and floating off to meditate musically by himself on Mars as a human god.
In other words, Romantic period musicophiles interpreted Beethoven as transcending all musical time and space to reflect on "eternal questions of music" at the same moment he was first able to write a single fragment of a "Mozartian" melody.
That should tell you something about the stature of Mozart.