Does dropbox have any weird quirks about shared files? I know googledrive teams was awful.
Most of my files by default in dropbox are accesible by anyone in my team, which is literally one person me. I could change ownership to only me, but I have to use the web interface and it is slow to respond to this instruction.
Although it is really odd that all of your files are showing as "Shared" if you're the only user on the account then it shouldn't matter. Make sure everything is encrypted and you should be fine.
Personally, I wouldn't like it and would figure out a way to change it. There is an admin setting to disable all sharing and that should fix this.
Pretty sure Dropbox counts everything as shared that isn't in your personal user folder that is automatically created for you as that's the only stuff that couldn't potentially be shared with others, either the whole team or selected members.
Does it really matter though if you're not sharing it with anyone else anyway?