My opinion.
In the 1970s and into the recent past, many bishops and parish priests were inclined to think of anything traditional as “old fashioned”, “out of touch”, “not today”, “oppressive”. A sort of trendy intellectualism also crept into the thinking, so that much of the “literalness” of old church design was rejected in favor of the “ultra symbolic”. As a consequence, those who controlled the funds and the projects tended toward the prejudices of the architectural world, which, at the time, was very much into Bauhaus-influenced design; a thoroughly secular progressive school. (Form follows function…leave that steel exposed.)
Architects themselves tend to view their work as a means of “talking to each other”, in much the same way as suburbanites “talk to each other” by the perfection of their lawns, landscaping, the country clubs to which they belong, etc., except that the conversation is conceptual in the case of the former. Those in power in the parishes and dioceses are “let in on” the architectural “conversation”. “This represents this…that represents that…the beams in the celing represent an inverted Ark of Peter…inverted to shelter the poor, etc, etc, etc.” Problem is, a lot of parishioners “don’t get it” and wouldn’t care for it even if they did.
At the core, it is, in my opinion, an elitist exercise on the part of those who, for whatever reason, do not like Tradition; usually in more ways than one.