Well, for one thing, there's absolutely nothing wrong with using a specific scale to play a song. Many artistes do that and they usually pull if off well!
I believe that since you know how to solo using certain scales and whatnot, I think you would you also know that having some form of melody is a good place to start. If you got a good catchy melody, chances are, you'll have something that should sound rather good! But then, how do jazz musicians and even Steve Vai, go about doing an instrumental, with so much doodling around? Yet still sound so good?
Perhaps what you need is something all of us regard as a must-have for every musician, and that is feel.
Check it out... we all know if you have feel, you can play Twinkle Twinkle Little Star and make it rock harder than any other tune out there. True? Well, okay, maybe not that song but you get the idea?
Feel comes about in various ways... vibrato is something that contributes a lot, note choices definately, phrasing is a seldom focused area and more. Sit back and think thru your technique, the way you hold your notes... do you find a lack of vibrato? Or you are just running up and down the scale mindlessly? Or how about your phrasing? How do you group your notes together?
Take some time to think about this then give a reply... I'll be ready to reply.