Unmerge the WoW and WoW Classic Directories
When WoW Classic launched, WoW and WoW Classic were separate directories. Today they are one in the same. This merge category causes headaches for users trying to find a streamer playing the version of the game they're interested in watching.
Sure, tags are there - but there aren't many streamers using the tags to deliniate which version they are playing. Currently, 24 streamers have Retail tagged.
My suggestion is to separate the categories, for a few different reasons:
User experience. Differentiating between the versions of WoW allow the user an easier path to finding a streamer that is creating content for the version of WoW they enjoy most.
Streamer discoverability. WoW is one of the busiest categories on Twitch with thousands of creators playing WoW and WoW Classic. Separating the categories would lead to less creators in each one, allowing viewers to find new streamers.
Consistency. WoW current exists in 2 states, 5 if you break it down further: Retail and Classic... or Retail, Classic, Hardcore, Wrath Classic, and SoD. Other games with multiple states have separate categories. These include CoD (Individual titles + Warzone) and Runescape (OSRS / RS3).
In summary, the goal isn't to completely decimate the WoW community, but make it easier for viewers to find streamers, thus increasing discoverability. Since WoW and WoW Classic are 2 separate games, in theory, it makes sense to have them be separate directories.