Okay, if it is easy to find a definition of socialism, please give one that would apply to the various strands of socialism.
As for the “official” quote here from the Socialist International, I’d be wary of just relying on any particular group to represent the whole (especially historically). I mean, would you rely on definitions or precepts drawn from the United Nations to represent the global community? But let’s look at what you cite from the Socialist International:
“Socialism aims to liberate the peoples from dependence on a minority which owns or controls the means of production. It aims to put economic power in the hands of the people as a whole, and to create a community in which free men work together as equals.”
Okay, I don’t see what is inherently unethical about this, and my first point was about the means of production: “Communal or state ownership of major industries and the major means of production.” In fact - and this is what astounds me somewhat - you do realise that for most of human history the means of production
was communally owned. Look at feudalism during the Middle Ages, especially in places like Russia.
And what does Pius XI condemn: “Because of this necessity, they hold that men are obliged, with respect to the producing of goods, to surrender and subject themselves entirely to society.” What does this mean, though? And do what extent is it the case? There are a variety of socialist responses. Very few socialist parties or ideologues are calling for the state or community to subsume
all the means of production; usually, it applies to the major ones. And if you’re going to condemn that, then you have to condemn Medieval Europe too.
But the social teaching exists and has to be followed.
I would argue that capital punishment is as much a social teaching as socialism is.
Furthermore, just because the pope says something it doesn’t mean it’s always accurate. He quote Pius saying that social welfare “leads to a loss of human energies and an inordinate increase of public agencies, which are dominated more by bureaucratic ways of thinking than by concern for serving their clients, and which are accompanied by an enormous increase in spending”. However, where is the proof of this? It may have been true 90 years ago but it doesn’t mean it’s true today. Moreover, some aspects of it might be true but the entire statement might not be.
If I reject Catholic social doctrine - which I don’t - without knowing what it says, I suspect you reject socialism without really knowing a lot about it either. I’d suggest reading some very interesting socialist writers such as R.H. Tawney, William Temple (who was Archbishop of Canterbury), Henri de Saint Simon, Frederick Denison Maurice (a theologian), and G.D.H. Cole.