DMARC happened 9 years ago, so I don't see why that would be related. I attended two universities in the United States, and they are both still happily forwarding emails to me. They have both been using Google Workspace for the last decade or so. So, for what it's worth, it seems like it's just your school that is doing this. Perhaps their IT department just has particularly dumb leadership that is trying to cover their ass for something they don't understand. Or maybe they have budget cuts?