What, does everyone need to be a mobile security researcher to care about security?

Most people can’t. But they can still choose options that are vetted by security experts in the community, and in the case of GrapheneOS also backed up by leaks from internal docs from Cellebrite, etc.

The main question is how is their security?

100%. I always ask people to look at their tax return. Does your money come from your labour/work, or from the things you own? If you aren’t living off of the things you own, then you are working class.