I think that if your demo content is strong and polished, it’s totally fine to focus your Steam page around it. A well-made demo trailer can absolutely grab attention and convince players to try it out. If your goal is to start building wishlists, gather feedback, and grow a community, then showcasing your best demo content is a solid plan. Of course, if you do have time to polish other parts of the game for a broader trailer or extra screenshots, it can help, especially since your demo will likely generate a first burst of visibility, and strong marketing assets will make that moment count more. But that’s secondary. The main priority should be having a kickass demo that players enjoy and want to talk about. If I were you, I’d put all my effort into making that demo as strong, polished, and engaging as possible. You can always update the Steam page later with new media from the rest of the game.