Piero,
I think the problem lies in the scene itself. I have sometimes witnessed a scene similar to yours in which a low-lying layer of haze separates the foreground from mountains behind it. To my eyes, the scene itself looks unreal, and the mountains look, in reality, as if they are pasted on! I have photographed some such scenes back in my film days, just because of this odd effect.
The trouble is: to any viewer who hasn't encountered a similar scene, a photograph will always look "fake." I think you should do the best you can with Janathan's suggestion, and then accept the photo for what it is.
I like it (partly because I've seen similar scenes.)
That's my 2 cents.
-Eric
P.S. A bit OT: On the LL forum there are often comments about photos that look "too digital." Just the other day on a walk I looked up at the sky (much blue sky with many white clouds), and my instant reaction was, "By golly, that sky looks digital!"