Look at who is on the board of Dropbox and ask yourself what the value of a file syncing service having accessibility (and previously kernel extension) privileges on your machine are.

Not to mention that Dropbox has never been E2E protected and had that Lenovo credential free access bug on web not too long ago.

Dropbox should be considered untrustworthy at this point, especially since iCloud Drive offers E2E encryption and so do other competitors.