Of course Android is not just that and I never claimed that. Are we talking about the security of the kernel or the whole OS? If you deem the kernel used in GrapheneOS to be sufficient for you, I’m assuming that it is the rest of the OS that concerns you. What in particular do you find to be good in GrapheneOS that SELinux with AppArmor and a trusted userland doesn’t achieve?
Good. Use something else if you can.