A few years back I came across this interview with one of my favourite guitarist, Marty Friedman. He had a few choice words to say about instrumental music, particularly instrumental guitar bands (of which there are thousands! )
At 4m45s into this clip, the interviewer asks if Marty has any advice to young players. Marty is quite critical of instrumental music and bands and he admits he isn't a fan of Instrumental and you know what, I totally agree. Neither am I. I find most guitar instrumental music boring to be honest, but there's more to it than that.
I personally think Marty's views about instrumental music are more about "instrument centric" instrumental music, IE the Joe Satriani's or the Steve Vai's type of instrumental. With myself as a guitarist being in an instrumental band, I have to agree with him. Instrumental music where the melody is all guitar is boring as these days and is like listening to paint dry. Guitar centered instrumental music has been done to death and most releases are quite narrow melodically.
There are of course a number of exceptions like Gutrie Govan's, The Aristocrats for example.
My band, The Cilikis, has moved away from our guitar centered music writing and I have deliberately pushed my guitar parts to the layering of the music. No one cares about the sweeps and taps and all the stock guitar wankery that you can do on a guitar, they just don't...
People want a great song that tells a story regardless of how good you are. You CAN keep an audience's attention if you are just willing to take the focus off your own playing and put the energy into the song your writing and keeping the musical story content interesting and diverse..
That doesn't mean playing different styles from one song to the next as Marty points out. That's more like a musical resume not an album. Instrumental song writing needs more attention than writing a song for lyrics. If you take out the lyric content, you need to do a lot more to win an audiences attention. Some of the greatest music ever written is instrumental music. Look at the orchestral greats and learn how they wrote instrumental music that still captivates people today.