You need both theory and practice together. Practice sharpens theory, theory guides practice. You don't have to be a grandmaster Marxist-Leninist with decades of theory under your belt to do good work. A large part of organizing involves training and educating comrades, for example, you even hint at it. Many orgs require a protracted training period before even being a full member, such as PSL or FRSO.

What's classist would be shutting out the working class from theory, keeping it purely for the vanguard. Many existing communist orgs have run into this problem, and resolved it in various ways. Theory is for the working class, not for a privledged few, so the good vanguards have managed to make theory approachable and digestible.