It’s common for people of a certain age (teenagers in the 1970’s) to say the only alternative to "guitar bands" (is that the term for that music now?) was Disco. But as others have already said, there were plenty of other choices. Of course, if you rely on the radio to know of them they have you right where they want you ;-) .
My God, there was John Hiatt, Ry Cooder, Dylan, Richard Thompson, Van Morrison, NRBQ, Tom Waits, Rockpile, Moon Martin, Marshall Crenshaw, Neil Young, The dB’s, Bonnie Raitt, Tom Petty, Dwight Twilley, Graham Parker, Elvis Costello, Mink Deville, Television, The Ramones, The Clash, Captain Beefheart, Cheap Trick, Squeeze, XTC, The Buzzcocks, Roxy Music, Patti Smith, Leonard Cohen, Loudon Wainwright III, ZZ Top, The Who (no Keith Moon, but still...), The Grateful Dead, thousands of others.
I suspect the defense will be that the above are hardly what teenagers listen to. It depends; my teenage friends and I searched out exactly those kinds of artists ten years earlier---we had to, we didn’t want to listen to what was being pushed on us. We discovered The Paul Butterfield Blues Band, The James Cotton Blues Band (Robben Ford was with him for awhile), John Mayall (with first Eric Clapton on guitar, then Peter Green), Albert King, The Bonzo Dog Doo Dah Band, Dan Hicks, Spirit, The Sons Of Champlain, Moby Grape. The Nice (Keith Emerson's pre-ELP band), Van Dyke Parks, Randy Newman, Jesse Winchester, Emitt Rhodes, The Flying Burrito Brothers, Commander Cody, Asleep At The Wheel, Fairport Convention, Mose Allison, John Coltrane, SO many others.
Well, weren’t we hip? Yes, yes we were ;-) . Guitar bands? Corny, man. I thought only girls liked that kinda music.