Based on some research and testing on the Spotify Developer console, it seems genres are hit or miss. Some albums contain a non-empty array returned in the JSON which contains genre(s) while others are empty. This seems to be regardless of popularity. I'll continue to investigate to see if there's something I'm missing in the API. If not, I can implement some light genre filtering on my own.
Based on some research and testing on the Spotify Developer console, it seems genres are hit or miss. Some albums contain a non-empty array returned in the JSON which contains genre(s) while others are empty. This seems to be regardless of popularity. I'll continue to investigate to see if there's something I'm missing in the API. If not, I can implement some light genre filtering on my own.