That is protecting capitalism. Social Democracy shields it from the effects of crisis. Look at FDR and his correct view that he saved capitalism in America. You tether a strengthened trade unionist aristocracy to your capitalist system and create enough of a safety net that it cannot be challenged. The ones exploited most or given no say are kept on the periphery and have no means of getting support from the other workers as they now have something to lose.

Good piece from Germany right after the real shift in terminology occurred https://www.marxists.org/archive/pannekoe/1927/sdc.htm

During its best days, social democracy established as its principle the class struggle against the bourgeoisie, and as its goal, the realization of socialism as soon as it could conquer political power. Now that social democracy has abandoned that principle and that goal, both of them have been taken up again by communism. When the war broke out, social democracy abandoned the fight against the bourgeoisie. Kautsky asserted that the class struggle was only applicable to peacetime, while during wartime class solidarity against the enemy nation must take its place. In support of this assertion he pulled from out of his sleeve the lie of the "defensive war", with which the masses were deceived at the start of hostilities. The leaders of the SPD majority and the Independents differed on this point only because the former collaborated enthusiastically with the war policy of the bourgeoisie while the latter patiently endured it, because they did not dare to lead the struggle themselves. After the defeat of German militarism in November 1918, the same pattern was repeated. The social democratic leaders joined the government alongside the bourgeois parties and tried to persuade the workers that this constituted the political power of the proletariat. But they did not use their power over the Councils and government ministries to realize socialism, but to reestablish capitalism. Besides this, one must add that the colossal power of Capital, which is the principle enemy and exploiter of the proletariat, is now embodied in Entente Capital, which now rules the world. The German bourgeoisie, reduced to impotence, can only exist as a peon and agent of Entente imperialism and is responsible for crushing the German workers and exploiting them on behalf of Entente Capital. The social democrats, as the political representatives of this bourgeoisie, and who now form the German government, have the task of carrying out the orders of the Entente and requesting its aid and support......

.....The social democracy has said that, in the current circumstances, after the terrible economic collapse, it is no longer by any means possible to realize socialism. And here we find an important distinction between the positions of communism and social democracy. The social democrats say that socialism is only possible in a society of abundance, of increasing prosperity. The communists say that in such periods capitalism is most secure, because then the masses do not think about revolution. The social democrats say: first, production must be reestablished, to avoid a total catastrophe and to keep the masses from dying of hunger. The communists say: now, when the economy has hit rock bottom, is the perfect time to reestablish it upon socialist foundations. The social democrats say that even the most basic recovery of production requires the continuation of the old capitalist mode of production, in conformance with which all institutions are structured and thanks to which a devastating class struggle against the bourgeoisie will be avoided. The communists say: a recovery of the capitalist economic foundations is completely impossible; the world is sinking ever deeper into bankruptcy before our eyes, into a degree of poverty which makes a break with the bourgeoisie necessary, as the bourgeoisie is blocking the only possible road to reconstruction ** So the social democrats want to first reestablish capitalism, avoiding the class struggle; the communists want to build socialism from scratch right now, with the class struggle as their guide.**

The social democrats of both tendencies, then, maintain the exploitation of the workers by capital; one policy leaves capitalism to its own development, the other stimulates and regulates this exploitation through the intermediary of the State. Both, for the worker, have just this one solution: Work, work, work hard, with all your strength! Because the reconstruction of the capitalist economy is only possible if the proletariat exerts itself to satisfy the demands of the most extreme degree of exploitation.