They have these things called midi guitars now. You don't need keyboard fluency. Hell, now a days you don't need any instrument other than a novation launchpad (a button grid). However, if you are going for a music degree, you should be able to know what the difference between a dorian and mixolydian scale. You should know that there's 7 different ways to play a D major on the guitar. You should know how to do pentatonic scales in any key as well as blues harmonic scales. Any guitarist who wants to play professionally needs to know this. Whether they are a rhythm guitarist, a soloist, a satanist, or a folk strummer. It's not just about being "gud", but knowing how to construct a solo, using those scales, in the songs key. That is very VERY much required. If you are interested in pursuing music as a degree then these things are table stakes. It's taught in high school. Go brush up.
what is a professional? Steve Vai? He knows all his scales. Eddie Van Halen? He's mastered scales at 12. Jimmy Page? ditto. Buddy Guy? He invented one.
If you're talking about a touring musician, or a studio musician, they absolutely know their scales.
Anyone who makes more than $20k/year with their guitar knows their scales.
Other cherrypicked examples, Dave Grohl and Clapton famously had no formal training and just learned by listening to and emulating artists they liked. I suspect they make over 20k/year.
Dave Grohl knows his scales now. Yes, if you make a band and become successful you can call yourself a professional without music theory. If you go back to what I said though, I said as a degree.
