If you're tired of Dropbox's "be the kitchen sink" mission statement, I've been using SyncThing[1] and it seems like a great replacement for Dropbox.
On Mac, be sure to install the cask version, which runs as an app: brew install --cask syncthing
A pretty good, basic blog post on how to set it up (but again, use the cask version instead): https://routley.io/posts/syncthing/