My opinion.
I don't use the term granny ring. Not because I consider it sexist or ageist but I always used 'the small ring' or similar. Just the way it evolved for me personally.
I have no problem with the term granny ring. I don't consider it sexist or ageist.
I've ever ever ever heard anyone in the real world complain it was sexist or ageist, the only place you'll hear someone raise the subject is on the internet.
If I did use the term in the real world, in the unlikely event of a single person complaining about the term, I simply wouldn't use it in front of them, just as a mark of respect. It wouldn't stop me using a word that IMO, has no malice in its use.
The internet isn't the real world...thankfully.