Bumping this, still very much needed feature for web developers who use Dropbox to store web projects.
xattr hack works by blacklisting node_modules, but whenever a folder is deleted you need to do it again, if you forget about it a lot of files gets uploaded so it takes a lot of time to remove, create a new folder again, xattr it and then npm install
The problem is much bigger especially on monorepo projects which can have multiple nested node_modules.