Who cares if it was for ads, giving third party companies access should be a huge problem with or without ads.
I always try to convince people I know to ditch Messanger/WA/etc. in favor of Signal, and in many cases I've succeeded.
I didn't win many over on the importance of privacy or Signal, but the willingness of some to put up with it because it matters to me says a lot about my relationship with them.
The state can make a duplicate of your sim at any time. Not to mention linking phones to people is relatively easy.