99.9% of consumers probably have never heard about custom ROMs, and I'd reckon 99.9% of consumers who do hear about custom ROMs have boring old fashioned objections like "will it break my warranty" and "if it ain't broke don't fix it" and "I wonder what's on Netflix tonight/I think I shall be washing my hair".

For the few people who distrust Google enough to install LineageOS or some such, they probably distrust Google enough to not care too much about not using Google. Who is in this sweetspot where they want (i.e. install and use, not merely aspire to installing and using) a custom ROM but having no access to proprietary Google APIs is a bridge too far?