It's a similar story on Android, too. (though Google Play doesn't break out current version vs all versions)

https://play.google.com/store/apps/details?id=au.com.dominos...

Having used the app prior to the change and after the change, I don't think it's just the switch away from native that is causing the negative reviews. It's that the website is essentially unusable without zooming in/out. I suspect that if they had switched from native to at least a site that had fit a webview nicely, the response may not have been negative at all.