I really don't think the benefit would outweigh the downside of engaging. At this point, it's obvious that these people have no credibility. As for those that wants to believe everything negative about Meghan despite common sense, they wouldn't believe KP anyways.
The best strategy is actually for the Sussexes to come back strong to work in the fall.
They have debunked false statements made about other royals. And as we see these small false statements can combine to create a false narrative.
They can't stop those people from talking but they can post a stronger defense.