Looking at their stock performance and the amount of work they’ve put into features that aren’t Dropbox file sync, he appears to have been right. iCloud doc syncing is what DB offered at that time.
I think he was right - now you've got OneDrive automatically bundled into Windows, iCloud in MacOS, Google Cloud in the Google ecosystem and Dropbox down 25% from IPO with no growth. I get nagging emails from them every month or so asking me to upgrade to a paid plan because I'll definitely not regret it.