These are deceptively difficult photographic conditions with what is probably one of the least accurate MFT lenses. I think that what the camera is doing is pulling out a lot of subtle shading under trying conditions. I have noticed that DPR has used this lense in the past, and I wonder if Oly's own superzoom performs any better.
I had the Olympus 14-150 for quite a while and it was much better at the short end but would have been, if anything, worse at this focal length. Actually, the trees in the distance look fine so maybe the focus point is off the main subject, visible even at this focal length and aperture?
It would look crisper with better control of chromatic aberrations anyway.
I liked the photo though.