与其说 + [description A],不如说 + [description B]
[subject] + 与其说是 + [noun A],不如说是 + [noun B]
与其说…不如说 sets two descriptions side by side and picks the second as the better fit: "it's not so much A as B". The first half is partly true but misses the main point.
The two halves are parallel: adjective against adjective, 是 + noun against 是 + noun, clause against clause. The subject can come before 与其说 or inside each half.
倒不如说 adds "actually", sharpening the correction.
The pattern is common in essays and reviews, and in careful speech.
Without 说, 与其…不如 chooses between actions: "rather than do A, better do B". With 说, it chooses between ways of describing something.
The description you reject goes after 与其说; the one you endorse goes after 不如说.