What you described about your friend is pretty typical protocol throughout the US and many countries. When someone comes to the hospital with Covid whose oxygen levels and/or symptoms at the time aren't yet severe enough to warrant admission, they are going to send them home to monitor and return if things worsen.
Hospitals don't have unlimited resources, HCP's, and ICU space to accomodate everyone that comes to the hospital for the past 1-2 years with Covid. What did you want them to do? Tell him to order a bunch of unproven supplements from Amazon to make it seem like they are doing something?
That isn't how medicine works. If you want to take supplements on your own given anecdotal info, go for it. You'll need a credible clinical trial showing something actually works to get an ER doc to send you home with a recommendation for a supplement, though.
It isn't our healthcare system that is broken right now. It is the ignorance and callousness of the general public who refuse proven vaccines over misinformation or political ideology and then show up at the hospital begging for the same medical community they ignored and marginalized to save their lives. Point the finger where it belongs, not those working themselves to the bone to help.