The main problem appears to have been the piano part. With the benefit of hindsight it may appear innocent enough, especially when set beside those by, say, Rachmaninov; yet at the time, the solo-sonata style Beethoven adopts for the third verse in particular was perceived as overbalancing the text.
Similarly the dramatic outpourings of that same verse, with its sudden changes of dynamic and the Mozartian Allegro molto final verse, were considered more suited to the opera house than the drawing room. This uncharacteristic outburst of theatricals may have been inspired by Beethoven’s studies with opera maestro Salieri (the legendary Mozart poisoner), although the songs of his old teacher, Christian Neefe (1748-1798), also leant in this direction.
from notes by Julian Haylock © 1999