What set Limbaugh off was the inclusion in the exhortation of the phrase "Trickle down". Trickle down is associated with Reaganomics, and with nothing else, and it presents the target of the Pope's criticism very specifically and clearly. For those who are not familiar with the concept, it is the idea that commerce benefits the poor by creating wealth in an economy and the poor involved in that economy participate, in the sense that a rising tide lifts all boats.
This is resisted by the more general claim (that predated Reaganomics and has outlived it) that commerce does not benefit the poor, and rather transfers wealth from the poor to the rich via profit. This sets up the idea of modern American dichotomy economics in which there are two opposing forces:
Profit, transferring money from the poor to the rich, and
Taxation, transferring money from the rich to the poor, via direct payments and Keynesian investment.
When you take one side in this debate, you alienate the other side utterly. Pope Francis definitely took one side in this debate. He criticized trickle-down economics and the "rising tide" claim. He did not criticize mandated transfer payments. He did not criticize infrastructure investment politics.
So, I don't think it's a matter of Limbaugh not comprehending the criticism.
Catholic social thought is, from what I know, definitely neither capitalist nor socialist
I think this present exhortation might not conform to that.