Hopelessly outdated?

We’ve used the Atahualpa theme since we made the jump to WP years ago. Loved it. However, having gotten security alerts that we needed to upgrade PHP from 7.0 to 7.3 to remain secure, our site no longer works. From what I see in the error logs, it appears to be related to compatibility problems between the latest version of Atahualpa 3.7.3 and PHP 7.3. Without updates, it appears you can no longer use this them responsibly and remain secure.