If there’s one basic foundation of 99% of all music, it is rhythm/groove. Rhythm is the “what.” Notes are the “why.” There has to be something before someone can ask “why is that there?”
It doesn’t matter if you only know the pentatonic scale, or are only capable of playing one note—you could play a great solo if it is rhythmically tight and interesting. Learning from bass players and drummers is a huge asset to guitarists and will make other instrumentalists want to play with you—not just other shredhead guitar players.
Young guitarists will often get googly eyed at the prospect of shredding—but you have to realize that to non-guitarists, shredding only sounds cool within the context of a tight groove.
Fareed Haque, a renowned classical/jazz/fusion guitarist tells a story about how there was this great rendition of a classical tune and he couldn’t figure out how the musician played it so fast. Upon further examination, this rendition was the slowest of the others he compared it to—what made it stand out was its rhythmic accuracy.
Metronome exercises are a great in the development of rhythmic accuracy, but most people like to overcomplicate things. Victor Wooten purports putting the metronome on 160bpm, and just establishing a groove—just a vamp. Slowly start adding fills—it doesn’t matter what scales or ideas you use, the focus is on rhythm. Then do the exact same thing at half the bpm at 80. Then after getting thoroughly comfortable, move to 40bpm. You progressively use less metronome so that the good rhythm comes from inside yourself.
If you have tight rhythm, people will be more apt to work/play with you then if you can rip scales at a million notes/second. Listen to percussive instruments and learn from them.