Aurora Store still works fine without the default enabled account sharing feature by creating an account for this purpose. Google hasn't blocked using Aurora Store as an alternate Play Store client. What's happening is that they're getting better at detecting and banning shared accounts. Account sharing was disallowed long before Aurora Store started using it as a way to bypass the need to make a Google account for the Play Store. Enforcement against account sharing has been increasing over time and we've been warning people they shouldn't rely on this continuing to work for years. It took longer than we thought it would to reach this point so our warnings were quite early.
GrapheneOS supports installing the standard Play Store app as a regular sandboxed app without special access. For people using sandboxed Google Play, we recommend the sandboxed Play Store for obtaining apps only published on the Play Store. That doesn't mean we recommend obtaining apps from the Play Store as the best option. We prefer people getting developer signed builds of apps, ideally through an app store with enforcement of standards such as a minimum API level and better enforced policies against abuse than the Play Store. Accrescent is very promising. There will hopefully be more serious Play Store alternatives to replace what it used to provide prior to them phasing out developer signed builds and beginning to gate access to apps.
On GrapheneOS, Aurora Store is mainly useful as a way to work around the Play Store having a way for developers to restrict their Play Store listing from devices not passing the Play Integrity device and strong integrity level.