The best thing I did was just use the guild section to suggest at the existance of themes, though I am sure there are other ways to set markers in the desert. Legendary creatures are particularly good at this, since they tend to draw attention, and they hint at a narrative string for each guild. I try to have the cube itself do most of the framing, going off of what I know about the people playing.
I don't have the best drafters in the world either, and with that, goes two things:
1. People don't really like being lectured about the "correct" way to do things, even if its objectively true. Explaining to a drafter what "negative variance" is just tends to make them feel stupid, and turn them off, so I would rather organically design in ways for R/W (for example) to naturally address bad drafting habits. Otherwise you're basically telling them that they are an idiot, and a bad drafter, even if you didn't mean to. I want myself, and the cube experience, to be an advocate for their abilities, not a missile that crashes into their world and upends it.
2. The written archetype breakdowns are hard to follow. Cube formats are too complicated for someone to objectively understand before entering, in the time frame they are likely to be alloted to look over the breakdown. I don't like feeding into that heuristic of "we're going to gain an objective understanding first and from that derive objective valuations for draft picks". I generally find that whatever breakdown you give them, they don't understand at all (though they will smile and nod through it in order to not look silly), they will struggle to remember and apply once put into the draft, and at the end of the day, will likely still depend on the draft itself to frame things for them.
Since I can't assume that pre-draft literature is going to work, I have to count on the draft to communicate its own potential.
Otherwise, you kind of just have to wait for the meta to evolve, or maybe cut things if its too stagnate for too long. At a certain point, people will get bored and start pushing the boundaries of things, and you want them to be able to see and be rewarded with something cool when that starts to happen. This can happen very slowly in our small playgroups.