Work profiles were never really designed for the user to keep things separate. It also requires using a third-party app as a device admin for the work profile, which therefore has privileged access to those apps, and means you need to trust an additional party.
GrapheneOS recommends using user profiles for additional segregation of your apps above and beyond the normal app sandbox. The development team have improved user profiles with features like notification forwarding between user profiles, and an end-session button to put user profiles at rest.
https://grapheneos.org/features#improved-user-profiles
The scopes features of GrapheneOS, currently storage and contact scopes, reduce the need for multiple user profiles to achieve segregation of apps beyond the normal app sandbox. With more scopes to replace sensitive permissions currently in the GrapheneOS development pipeline, the need for separate user profiles will be reduced even further in the future.
https://grapheneos.org/features#storage-scopes
https://grapheneos.org/features#contact-scopes
Last but not least, GrapheneOS also adds the ability to disable user-installed apps, which completely stops the app from being able run: https://grapheneos.org/features#user-installed-apps-can-be-disabled
All in all, work profiles are not something that GrapheneOS is focussed on. Instead the development team work to provide private and secure devices through a number of featues, including improvements to the app sandbox, permission scopes, and better user profiles. See the features page for more information: https://grapheneos.org/features