As others have mentioned, this is a personal opinion-type of question. Any instrument can be difficult if you aren't interested or motivated to practice and learn the unique characteristics of whatever it may be.
When I reached the point in my piano lessons where both hands were playing at the same time but were playing different notes and rhythms, I wrote in my lesson book in my boldest second grade printing, "THIS IS HARD!" (I still have the book!) Since then, I have progressed on from that point (thankfully), but I can still vouch for the challenge of playing a piece well.
I am amazed when I watch my church organist playing two of the three keyboards on our church organ and using her feet to play the bass pedals at the same time! Again, I understand that it's a matter of practice and experience, but that takes a lot of coordination!