Why Trine 3 is so simple

[iivietal]

I'm waiting Trine 3 for a long time. The graphic is still amazing, the gameplay is smoothly. But I think it is so simple. It's shorter and easier 2 previous version. There are no skill tree, it's ok, but the characters are missing almost interesting skills from Trine and Trine 2. Beside the boss, the enemies are too simple too.
And the story just ends like that? Now I'm waiting for Trine 4, or DLCs?
I love Trine series, but Trine 3 makes me disapointed.