After doing some research i've come to learn that MJ was not a serious instrumentalist by any means. He could play very basic stuff to get ideas accross but not to a high standard. Also checking the album credits MJ played very basic instruments like the slapstick, if he was an amazing piano player, drummer, guitar plater etc he would have played on his songs himself instead of getting in other people to do it for him.
Now i know that alot of you will say ''He got a guitar playing credit on Morphine'' but it has been said that MJ's guitar credit there was for his beatbox. Also showing pictures of MJ holding instruments don't prove anything. He could have just been posing with them
Also if you listen to MJ when he talks about his songwriting process he says that he makes sounds into a tape recorder and then he goes into the studio and gives the musicians all they're parts. Go and listen to The Girl Is Mine Mexico Deposistion on youtube and that video shows MJ composing The Girl Is Mine and not once does he play an instrument. He just used his vocals to compose the music.
I'm not trying to take anything from MJ talent away. He was an amazing singer, Songwriter, dancer and producer but he was not the greatest instrumentalist. Plus playing instruments and composing music don't always go hand in hand. You could be the greatest multi instrumentalist in the world and still be a crap songwriter. MJ had a fantastic ear for music and knew exatly what he wanted and he used his voice/beatbox to accomplish this