I said that inverting base and superstructure is idealism. It is a tautology so it shouldn’t be mind boggling.

I didn’t say that common law is some utopian system of law, or that it is superior to civil law. I only explained why it exists and why it’s not absurd per se.

Since it is a question of separation between legislative and judicial power, the common/civil law divide doesn’t really map to a divide between capitalist and socialist law. Depending on implementation and circumstances it can be good or bad, for example common law can be used either as a tool of judicial reaction against a progressive legislature, or as judicial progress in context of a conservative legislature.