While Pope Saint Pius X and Pope Benedict XV simply continued and according to some even moderate Pope Leo XIII’s stance in favour of moderate/conservative Capitalism, Pope Pius XI expanded on and even altered the emphasis of Catholic social teachings in 1931 with Quadragesimo Anno. The encyclical, which came in the midst of the Great Depression is extremely fascinating today both for the various ideologies it condemned, the economic options it left open and for the historical impact it had.
While Rerum Novarum had rejected merely unbridled/unrestricted Capitalism and advocated for certain reforms of the existing economic system (without the state if possible), Quadragesimo Anno envisioned various forms of greater and even necessary state intervention even while continuing the uphold both private property and a condemnation of extreme Statism.
In certain areas Quadragesimo Anno doubled down on the stances expressed in Rerum Novarum including its condemnation of socialism and its defense of private property.
Pope Pius XI acknowledged the separation and differentiation that had occurred between communism and socialism.
He condemns communism as being exceptionally violent and causing destruction while dealing with moderate socialism (including social democracy). While some socialists had rejected class struggle and attacks on private property, others had only moderated these anti-Catholic positions. But even moderate socialism in the classical (leftist so excluding so called “conservative socialists) was still rejected as incompatible with Catholicism in unequivocal terms, and Christian Socialism (a weird mix of Christianity with leftist/classical socialism) was called a contradictio in terminis because its desire for state ownership over the means of production and its general utopian aims were materialistic and came at the expense of important human values like liberty.
With both communism and leftist socialism condemned in all its forms, Pope Pius XI specifically named (economic) liberalism for the first time and condemned it as well. At the same time he specifically affirmed Capitalism was not in and of itself contrary to Catholic teachings but that unbridled Capitalism was. He went further and pointed out how excessive capitalism ironically undid the free market and resulted in an economic dictatorship where certain people with key roles in the flow of money influencing the political system (Crony Capitalism).
Not only was the defense of private property repeated but it was even affirmed that the government couldn’t violate it because property was not used or not used properly and that there was a right to pass on property through inheritance. A misuse of scripture to argue that only workers were entitled to the profit of labour and not those who provided and managed the means of production was rejected.
State ownership of certain key elements of the means of production is also affirmed. The decisive influence over the means of production though not general ownership does reside with the state.
The usage of property as opposed to its ownership was not treated as sacred. The use of property involved interaction with others in the public sphere. The absolute sovereignity of the free market was rejected.
Economic internationalism and especially international imperialism were condemned and at the same time economic nationalism and especially economic imperialism. In the same vain, both pure individualism and collectivism were condemned.
The profit motive and the desire of the rich to become even richer was respected but it could never come at the expense of the basic rights of others or be achieved through illegitimate means.
Contrary to Rerum Novarum Quadragesimo Anno felt ready to support labour law and state enforced minimum wages.
Pope Pius XI provided a more narrowed down system for the Church to supported, regulated market Capitalism with near absolute private property and the possibility of more centrist state policies to provide meaningful jobs.
He could have left it at that, but instead he added the concept of subsidiarity, that in as much possible, responsibilities for economic and other social matters should be devolved to as local and personal a level as possible, which would become essential to various Christian Democratic movements.
Next, he even explored multiple third position economic systems as well.
While re-affirming that the wage system is valid, Pope Pius XI views co-ownership of businesses by the workers desirable.
The bottom up corporatism that took inspiration from the medieval guilds and was practiced by Salazar and proclaimed by Dollfuss finds the strongest endorsement possible. 
Pope Pius XI also dealt with the tripartite/statist corporatism and national syndicalism supported by fascism. He noted the positive aspects, including the successful suppression of socialist groups and class cooperation that it facilitated, but acknowledged the state also assumed a very interventionist role that could appear to largely serve political ends. He ended the nuanced assessment by asserting the need for it to be blessed by God and supported by proper Catholics for it to work.
In the anti-communist encyclical Divini Redemptoris in 1937, Pope Pius XI expanded on the possibility of state interference in the economy by allowing them to tax the extremely rich to provide for the public good when necessary.
75. It must likewise be the special care of the State to create those material conditions of life without which an orderly society cannot exist. The State must take every measure necessary to supply employment, particularly for the heads of families and for the young. To achieve this end demanded by the pressing needs of the common welfare, the wealthy classes must be induced to assume those burdens without which human society cannot be saved nor they themselves remain secure. However, measures taken by the State with this end in view ought to be of such a nature that they will really affect those who actually possess more than their share of capital resources, and who continue to accumulate them to the grievous detriment of others.
When the dust settled, the following was clear to the Catholic world:
Communism (extremely harshly)
Socialism in all its (classic/left-wing) forms
Liberal, individualistic, international, imperialistic and Crony Capitailsm
Regulated market Capitalism with some state welfare, public sector in key areas and labour law (subsidiarity is appreciated); (non-totalitarian) Dirigism, Social Market economy/Rhineland model, Polder Model etc.
Tripartite (Fascist) Corporatism and National Syndicalism
All this was tot he anger of communists and socialists and inspired various politicians from FDR to Salazar and Dollfuss. Moderate variations of Capitalism and different forms of third positions economics were analysed and promoted by the Church while classical left-wing economics were again condemned.
- Quadragesimo Anno, 112
- Ibid, 120
- Ibid, 101
- Ibid, 88
- Ibid, 114
- Ibid, 64-65
- Ibid, 81-87
- Ibid, 91-97