Well thanks for the replies. I still can't square "ideas only exist objectively in practice," which is (IMO, but apparently nobody else's) a critical insight from Marx; and "the theory" being something that is inherently unknowable except in the most abstract lines of comprehension. Communists literally never spend time theorizing what the future society will be like. I don't understand how we are defined by something we can not understand concretely, as well as an activity that not only do we not engage with, but comrades will literally discourage, preferring to engage with actual struggle.
When I work with a lot of new people who want to get involved in practical work, the way to get them and keep them active, is not to describe the theoretical future, but connect them, their ideas especially, with the present. But when left to their own discussions, they often wax on about how things "should be". So is it practical to connect with them on that level? Absolutely. Is it what makes me and my comrades "communist?" No, what makes us a communist is the work we do, not the dreams I dream. That "work" can be self-development, and it can be development of objective conditions, and at some point self development and development of objective conditions become one in the same.
But either I don't understand something or other people don't understand me, and I wouldn't begin to know how to tell the difference. The other commenter was just debating me, so I'm not really any further along. But thanks again.