Some part of the post-Vactican 2 liturgical changes called for decrease in icons and statues so to not “confuse the faithful.” In regard to the OP, this didn’t help. I can’t remember which Consilium document this is laid out in.
EDIT: The Constitution on the Sacred Liturgy, paragraph 125 reads:
The practice of placing sacred images in churches so that they may be venerated by the faithful is to be maintained. Nevertheless their number should be moderate and their relative positions should reflect right order. For otherwise they may create confusion among the Christian people and foster devotion of doubtful orthodoxy.
This is pretty vague (like most of the document), and I’m guessing was interpreted as a call for bare walls. I am not sure what the last line means or what it implies with regard to existing Churches, devotion to Saints, and subsequently teachings of the Church. I’ve never heard of any icons causing rampant devotion of doubtful orthodoxy.