As others have said here, these are not apps that have been developed by GrapheneOS, but rather are default AOSP apps. They haven't gotten UI updates in years, which is why they look "ugly".
If you want an example of apps developed by the GrapheneOS team, look at the default camera app, or the "Apps" app repository client application.
Replacing these AOSP apps in the long run is wanted, but the resources to not only develop but keep those apps maintained beyond that is not insignificant, which is why it hasn't been done yet, as the team has prioritized working on features like Sandboxed Google Play, Storage Scopes, Contact Scopes and others.
You are free to install any apps you want in their place. The team adopting 3rd party apps isn't a solution because those apps typically have incompatible licensing, a different approach to security (or a lack thereof) or other issues. The solution will be for the project to design its own set of apps, but this won't happen overnight.