I believe the main source of disappointment with TS4 mermaids is the same as others have already pointed out - no underwater diving gameplay/exploration.
While I highly enjoy the customization and some of their powers, not having at least a SINGLE underwater lot for both mermaid and diver exploration/gameplay was a huge mistake to me. Diving being a rabbit hole is just really disappointing. Seems we are once again back to making underwater lots through the console...
I don't think this will be a problem for Realm of Magic though, mostly because it doesn't require something as big as diving/underwater mechanics, it's mostly just spells and potions/some magical interactions. Given that it's a GP fully focused on what seems to be Witches, I don't expect it to lack depth.
I will most certainly be pissed if they don't include a flying broom interaction,mechanic that lets us at least hover around the lot.
