I think they look fine too. Maybe use more deeper shadows to give some more depth.
Like...plan out which clouds will be in front and make those brighter, giving them not as deep shadows as those in the back. I guess you will get a more overall depth, so they will seperate more into 3D. You did that already a bit.
What i always find fun on clouds is that there are faces and funny things to recognize.
Do you see that little Godzilla and Witch/Ogre? :D Hehe, i see a sleeping swan, an Antlion, a disfigured Winnie Poo and more. So fun.