Featured pale blue color feels like it doesn't fit for Materia (but I understand why, I haven't been able to find a good one just playing around)
The rounded dotted line also doesn't feel like it fits Materia - We're not using dotted lines anywhere and the radiuses (radii?) we use aren't that large.
Drop shadow on the cards feels heavy, maybe tone it down? Or switch to a slight border?
The hide animation on the cards feels a little janky, when removing a lot of cards due to a search there's a lot of movement happening. Leaning towards no animation, or if we keep it, maybe a longer debounce before the cards transition between existing and hiding.
Widget Catalog and Featured Widget headings I think should be Lato, and the gray feels too low contrast