All the benefits of "cloud", but you know where your data is. Do remember to make backups, but you need those for commercial services as well.
That said, the security issue wasn't really the fault of OwnCloud. They use a Microsoft library, which itself included a further library. That downstream library had the security issue. Unfortunately, it happened to interact especially badly with the containerized version of OwnCloud.
That kind of downstream security issue can bite any project. I don't blame OwnCloud in the slightest, and they were very quick to acknowledge the problem and post the solution.
Do not allow access to owncloud without a vpn!!
I know it is only anecdotal, but I have been running OwnCloud for many years now, available without a VPN, with no security problems.