You might just be too early right now. VR headsets just aren't very popular. Personally, I find the hardware atrocious and am waiting for someone like Apple to "do it right". As a late adopter of VR, I may not be your target audience, so take what I say with a grain of salt.
I was surprised you didn't have any videos of interacting with OpenBrush on your home page. Normally, I would have clicked away if I stumbled on that page, but since you posted on HN I searched it up on YouTube.
Do you and your volunteers use Open Brush regularly? If so, toss up some casual live streams on Twitch or other platforms. Post on Twitter and Discord, etc. before you go live, then upload the recording to YouTube for people to watch later.
Part of what makes Blender so damn accessible is the huge number of YouTube tutorials. Virtually every feature of Blender has at least one high quality tutorial video, walking people through every step.