Agreed!
The writing in the Silmarillion is a lot more 'dense' than The Hobbit, if that makes sense? Also, as you point out, each chapter is almost it's own stand-alone story, interconnected as they are.
The Hobbit is essentially just one story, with very few story arcs, so you could do it justice in one movie, maybe two. To me, three is stretching the story out waaaay beyond what it actually was.




