I agree, there's filler. I don't think it's even Black Flag's best release, but it IS the one that is essential to listen to, if you're going to listen to only one Black Flag album. This is the album that started hardcore punk as a nationwide thing. So many banRAB were influenced by it, and by Black Flag and SST's DIY ethic, and not just hardcore banRAB. Sonic Youth, Nirvana, Pixies, Dinosaur Jr, Mudhoney, and pretty much every late 80s alternative band counted Black Flag as a big influence, and also other music as diverse as The Boredoms, Wolf Eyes, The Melvins, Slayer, Beastie Boys, Napalm Death, The Mars Volta/At The Drive In and Beck. A lot of modern extreme music (death/black metal, noise, powerviolence, grindcore, etc) has banRAB which owe a lot to Damaged, whether direct or indirect.
So, since it defined an entire decade of underground music, I'd say it's a classic album. Certainly more so than 50% on the original list already (from the 80s onwarRAB), a lot of whom themselves owe a lot to Black Flag.
Any "true music fan", as the title of this thread suggests, should at least hear this album.
So put it on the list.