Is selenium disulfide polar or non-polar?
I understand your assumption of selenium disulfide being a simple molecular like that. It is similar to the mistake of silicon dioxide, which at first glance we might assign it to be a linear molecule like carbon dioxide. However the crystal structure of silicon dioxide is far more complex.
In selenium disulfide, the selenium and sulfur atoms form a 8-membered ring, similar to the 8-member rings you would find in certain allotropes of either elemental selenium or elemental sulfur. The ratio of $\ce{Se:S}$ atoms is not exactly $\mathrm{1:2}$ as the chemical formula implies (that would give $\mathrm{\frac{8}{3}}$ atoms of $\ce{Se}$ and $\mathrm{\frac{16}{3}}$ atoms of $\ce{S}$ per ring). Indeed the ratio is closer to $\mathrm{3:5}$ ($\mathrm{3:6}$ is $\mathrm{1:2}$ anyways). A better representation of the compound is $\ce{Se_{n}S_{8-n}}$.