It's also not like there are no problems outside medicine caused by the current situation. A hackathon won't solve those either, but can provide exactly the mentioned space to experiment and communicate can be the starting point for larger projects. I think the big recent ones didn't do a particularly good job at pointing people in the right direction though, so there's been a lot of projects that indeed seem questionable.

I.e. the platform that sprung up that crowdsources which stores etc closed and which didn't doesn't heal people, but has been quite helpful to find something I needed urgently. The grassroots effort that filled gaps in the PPE supply by scaling from a few hackerspaces doing 3D printed faceshield holders to organizing companies and community spaces to get parts injection-molded, material distributed, and shields assembled in the thousands is exactly about finding and connecting people with the right skills and resources. etc...