GrapheneOS says Google is making life harder for rival operating systems and devices
(www.androidauthority.com)
To be honest, I think for the average user most ROMs are more than secure enough. And from a privacy perspective a lot of the de googled ones are very good.
Grapheme has almost a cult following in a way that its all or nothing.
I'd rather give up a bit on security while preserving privacy, if it means my money does not support terrible companies.