Liberalism was pushed by capitalists in fighting the aristocracy. In that sense, it was progressive, but only in that context. Now, it's outstayed that welcome, and is used to fight against progress. We have lived up to the constitution, it was designed to protect capitalist profits and rule as a settler-colony founded on genocide.

As for communism, the various socialist countries have lived up to Marxist ideals. The problem is that, at least in the eyes of some typically western communists, socialism in real life means having all of the struggles and imperfections that come with being real, and these imperfections can't compare to the perfect, almost religiously pure ideal of socialism in western leftist heads. If we uphold Marxism correctly, we support this existing socialism, warts and all, for being dramatically progressive and liberatory for the working classes.