GrapheneOS will have extreme difficulty being taken seriously while they are "you need to buy Google hardware to run this" project. This is why GrapheneOS has a tiny userbase.
Also, GrapheneOS has plenty of users, and we're growing fast. People appreciate quality.
GrapheneOS is not going to compromise on privacy or security, and so far, pixel devices are the only devices meeting the hardware security requirements. People have not had an issue taking that seriously.