I’m honestly surprised Apple didn’t retire the Siri brand.

At this point, “Siri” has a pretty strong cultural association with being underwhelming or unhelpful. Even if the new version is dramatically better, convincing people to give Siri another shot may be harder than launching the same technology under a new name.

Feels like a missed opportunity to reset expectations.

Yeah missed opportunity. They could have even had a fake funeral for Siri like Jobs did for OS 9, or a "retirement party" or something. Leave the Siri brand behind and launch this as something brand new.