This is a configuration issue. Onedrive also supports OTPs.

But regardless, what alternative would you propose? Did it contain any sensitive information? Does the alternative integrate with your current system? Do people need to create accounts for it like Dropbox? Do I have to teach all of the employees how do use this new service instead of just right-clicking and sharing the file?

SFTP is a no-go for obvious reasons. I can't even get people to stop clicking birthday initiation links from Australia (we're in the US) let alone teach them how to use FTP.

Dropbox would require a dropbox account. 100% not going to push another piece of softare on them when our current software already does.