You don’t have to, but you should. Lenin and Mao practically worshiped Marx and they both attempted to implement his system faithfully to the spec he advocated for. And I know that viewpoint is somewhat controversial in non-Leninist/Maoist circles but I think it’s true.

What’s more I think the historical records of economic collectivism outside of Socialism and political Authoritarianism outside of Socialism are numerous and expensive enough to justify an opposition to Communism as a system.

I think the main realization that made me nominally support Capitalism is it’s performance in a “degraded” state. You can have the absolute worst scenarios (think Pinoche Chile) and Capitalism provides constant incentive to improve things and doesn’t seize up in the meantime. It continues to function even in the face of severe inefficiencies.