This sounds like a whiggish progressive distortion of history.

First, the Church isn't in the business of policy. The Church recognizes the distinction between secular and religious authority, and indeed, it is the origin of that distinction, from which the exaggerated liberal separation of Church and State comes from (you won't find this distinction outside of Christianity, and indeed it makes no sense outside of that context). The Church will advise or comment or respond to policies as a moral authority, but policy as such does not belong to its scope.

Second, Catholic Social Teaching didn't materialize out of thin air. It is a culmination and explicit formulation of millennia of teaching. The industrial, political, and economic upheavals of the modern era are what motivated this explicit formulation.

Third, I wonder what you consider as "reactionary" here. The term itself is an incredibly loaded and condescending progressive term and takes for granted the correctness of the progressive view. The Church has been consistent in its teaching. It does not adapt to what is fashionable or to ideological fallout (even if particular prelates may show signs of doing so).