I'm going to try spin some of the comments into an answer, even if this does eventually end up being marked as a dupe of Why are my photos not crisp?
From your settings, 1/1000s, f/4, ISO 100 at 18mm then motion blur is probably not the principal cause. Autofocus error is a much more likely candidate.
There is some slight aberration at the edges of the frame, but I don't think this is a major issue, considering the focus is off.
Wide angle lenses don't really lend themselves to beautiful bokeh anyway.
It looks like the camera chose the woman in left nearfield as the point of focus, which then will leave the entire 'subject' ie the garden itself, out of focus.
After comments - I think it's quite possible that the autofocus selected the woman whilst she was closer to camera. She then took another pace or two before the shot was taken, leaving even her just slightly out of focus too.
Practically, this could have been ameliorated by either forcing the camera's focus point to a specific area of the frame, or by manually focussing somewhere in middle distance. At 18mm f/4, any focus point more than 5m away would be as close to infinity as makes no difference for anything over 2.5m away.
Opening the aperture still further would have softened the foreground, which may have better pushed attention towards the garden itself, & softened the foreground distraction.
Aesthetically, I'd have waited til she got right out of the way.
Even in a busy place sometimes standing there for 5 minutes might give you just one good opportunity with no-one near enough to distract..
 See the DoF calculator at Cambridge in Colour