I think the clearest distinction of idolatry is mistaking the finite for the infinite.
Which would indicate some degree of what's in the subject's mind matters and that it can occur with pretty much any finite object, including even a Bible.
or as I attempted in my bad typing and worse proofing, confusing the difference between a creature and The Creator.
For most of us we look around and see youth, sex, beauty, power, money, the nation, a political system held in people's hearts in the place where we think God belongs. And we say, "Idolatry" but while we do think there's a soul-wounding effect of such disordered allegiance, we don't tend to think that there is a numenous thing, a small-g 'god', associated with that attribution of worth, that worth-ship.
So those who think we are idolaters and worshippers of false gods probably think we wound our souls by giving worship to Mary, who is NOT intrinsically divine. Would some think that we are in fact worshipping demons, I wonder? That is to say, do they think we are in some kind of communion or attempting some kind of communion with spiritual entities who are not playing for God's team but who, between now and the eschaton, have some power to wreak harm?
But to get back to your comment, yeah! And what should resonate in the hearts of each of us when the sola fide gang speaks is the EXCELLENT admonition NOT to worship to work of our hands. Proper Veneration for Scripture can be a great opportuniy to start worshipping one's own orthodoxy or Faithfulness in Bible Study or whatever. "Oh deliver me from my secret fault," (the one I've been doing for ever and am not even aware of ).