Sure, usability might not be perfect because Google only releases base Android as open source software and keeps all their fancy apps proprietary, but it's not in a state where it's totally unusable either.
Agreed. GrapheneOS/AOSP feels a bit like desktop Linux, where the base OS is there but many components like screen time have to installed seperately (e.g. screen time/app usage). Compared to many phone manufacturers installing apps for ads or other unnecessary bloat.
That's why Graphene allows you to disable the security features.
That's what I did the second time I tried GrapheneOS. The worse ootb performance made me install CalyxOS again, until I found out Secure App Spawning can be disabled.