Yeah, but I think the hook of unlocking/finding more spirits actually works quite well, see the awesome Orca thing I saw yesterday and would like to find. As it seems, you'll be unlocking more Rs to summon until you freed all areas, so you might always have something new to look forward to.
The raids could be more interesting, I give you that, but if I am being totally honest here, I would have expected an F2P game like this to be without something like the raid system because the raid system gives you extra benefits and playtime without touching the other F2P elements. I am usually doing 2-3 levels, 1 raid, 2-3 levels, 1 raid etc, which gives me nice and fulfilling 2-3 hour play sessions without the feeling of being stopped in my progress by an F2P barrier (pay to play more!)