I like them both.
Though I think Frozen Ever After is the better attraction.
Mermaid doesn't have much to do with CA on its own, but it feels thematically appropriate in a larger area that does. It's a clever way of integrating IP into an area without it feeling like they're trying to jam a square peg into a round hole.
Like most people when it was announced, I was upset with the idea of Frozen Ever After but after actually riding it, I found it hard to dislike. I suppose I can see why its inclusion makes others upset but as long as the greater showcase being discussed still feels like Norway, Mexico, United Kingdom, etc., and not Arendelle, Santa Cecilia, Hundred Acre Wood, etc. then I'm cool with it.
If infused properly, those "Disney" themed attractions sort of kind of make you think about how the general culture or people from an area have inspired the art of film and how through it, we are able to share our cultures and stories with one another in a way that's fun and accessible. -and at the end of the day, isn't that what World Showcase is really all about?
Of course, the inclusion of something like Frozen Ever After or Remy's Ratatoullie Adventure pushes merch and digital subscriptions for Disney, it's true. But if it also inspires even a handful of people a day do want to see Norway or Paris for themselves someday too, then I'd argue they're fitting right in.