Well, that all depends on what you mean by “scripture” and what you mean by “relevant.” At least according to some people.
As far as I can tell, they don’t really engage the question directly, so let me help.
The essential question seems to be this: The perspective being proposed by many liberal Mormons is that scripture is a text that we as individuals and as a community believe to be scripture. Its scripturality derives from the status that its believers give to it. Of course this is an obvious tautology. The Bhagavad-Gita is scripture because Hindu’s believe it to be scripture, and the Qur’an is scripture because Muslims believe it to be so. The real question is whether that is all scripture is. It makes a huge difference if the Qur’an is a collection of the opinions of Muhammad or the eternal word of Allah, a question that is not dependant on what Muslims might believe about the Qur’an.
This perspective ignores that scripture is scripture because of something in its nature and essence, not in our response to it. It is and remains scripture even if no one believes in it. Scripture is a manifestation of God to humans that humans can accept or reject. But human rejection of scripture does not change its scriptural nature; that comes from God. Scripture is scripture whether we believe it or not.