I got some good advice from some pros that you may be able to find inspiring. One of them is one of Syn’s biggest guitar heroes. I watched a Dimebag Darrell masterclass where he’s demonstrating what he does with scales. I KID YOU NOT, this is almost word for word what he said when someone asked him about how he writes his solos; he said, “I don’t know much about scales or theory (plays a pentatonic scale) I mean I know this is a pentatonic scale. But I just play what sounds good.” And that’s Dimebag – one of the biggest guitar players of all time.
Another one is Marty Friedman. I watched a Youtube video of him and he said, “I like to create my own scales. Sure I know theory. But it takes a lot of time to sit there and study every scale. So I like to play a chord (plays an Amajor chord) and immediately after I like to make my own little scale of what sounds good over it. (Plays chord then plays “invented scale”) I mean I’m sure that scale has a name, but I don’t know it. I just know it sounds good.”
Also, look at Syn’s writing process. Especially in City of Evil. I mean sure, the guy knew theory. But when you actually sit down and try to dissect his solos and songs, they change key signatures a lot and his scale usage is all over the place.
In conclusion, I feel that knowing TOO much theory can make you follow the rules ‘too much’ and can make your songs sound mundane and monotonous. Sure classical composers really knew their stuff but they also had things like first movement, second movement, third movement, etc where things got changed up a lot. Many amazing legends don’t know much about theory at all. And if they do, they only know a decent amount and learned it through the years instead of having to learn it first and THEN write a song. But I agree with Vasrely. It does make it easier. I hope this helps