na-adjective
flat; planar
Describes something physically flat or two-dimensional, lacking depth or three-dimensionality.
この絵は平面的で奥行きがない。
This painting is flat and lacks depth.
na-adjective
superficial; surface-level; one-dimensional
Used figuratively for ideas, analysis, or people that lack depth or nuance.
彼の考え方は平面的すぎる。
His way of thinking is too one-dimensional.
その記事は問題を平面的にしか扱っていない。
The article only deals with the issue superficially.
Means 'superficial' or 'on the surface', similar to the figurative sense of 平面的 but more directly about outward appearance.
From 平面 (flat surface) + 的 (-like, -ish).