This has been my most commonly asked question since the series restarted, and it's for a few reasons.
First, we've seen Dana fight every kind of monster, god, demon, alien, and robot over the years. This allows Rita to try it, while Dana snipes from the sidelines. It also lets me shake up the dynamic without nuking the cast. Dana, Rita, Titania, Dr. Shark, everybody's still here, just recentered.
And finally, handing off a mangled legacy to a new generation and saying “good luck!” feels pretty recognizable right now.