because humans have differing experiences

Nuh uh! All sub-categories of people are monoliths, and each individual is an exemplar.

Though I imagine it depends on how we define authenticity.

Totally. For me it just means that readers from that group would generally feel that it captures the essence of their experience. Which, of course, is not a guarantee even if the person writing the story IS from the group in question, because humans have differing experiences. I’ve seen it done in groups that I am a part of, but it’s certainly hard. I agree with you that it should be done with caution.

I don’t think it’s a prerequisite to authenticity

And I disagree, which is fine. Though I imagine it depends on how we define authenticity. A story being compelling isn’t the same as a story being authentic, for instance.

ETA: We could have this discussion for months, but as it applies to MUing I’d say simply that one should be careful they aren’t using their diverse character to speak over, or for, the people said character represents.

as they lack the kind of lived experience and personal connection that lends authenticity to those stories.

While I agree that experience and personal connection can deepen a story, I don’t think it’s a prerequisite to authenticity. Imagination is central to writing. There have been plenty of compelling stories of people with differing genders, ages, cultures, etc. as the author. Even non-human characters.

Whether an author should attempt to tell a diverse story not their own is a touchier question, and not one that I feel has an easy answer.

Translating that to MUing, though, is tricky.

Back in the early 1990’s I played a Jewish character and made some comedic mistakes about traditional Jewish weddings.

The guy who played Blaze the infamous gay werewolf played gay characters who almost certainly would have been offensive in the hands of a straight player. But by and large I’ve not encounted badly done MU characters who belong to demographics I share. How about you?