You don't see anything except Linux discussed on Lemmy because Lemmy has a couple thousand active users. There are Facebook groups bigger than the entire fediverse.
I think you're missing that lemmy is a pretty tiny slice of the internet and niche(ish) communities either don't exist or are mostly inactive. Just because something doesn't seem to be making waves on lemmy, doesn't mean it isn't popular. The community for it just isn't really here (yet).
WoW hasn't been synonymous with the MMORPG scene since at least the last 5 years. You didn't hear much from it because it's just another expansion, for one of the many currently running MMOs. When was the last you heard about GW2 expansions? Or Elder Scrolls Online expansions?
Just because people still log in to grind dailies and world quests doesn't mean the game has the same presence in pop culture it used to. I remember seeing commercials with Ozzy for wotlk, people would talk about the game, you'd see references to it, there was a south park episode about it.
It's just not that relevant or popular anymore.
You don't see those commercials anymore because television isn't relevant anymore. The internet is full of ads for the new WoW expansion, just like it was full of ads for the new XIV expansion and ESO expansion when those released.
I consume as much media as anyone, a lot of gaming content, and I don't recall seeing a single WoW ad in years, not on websites, youtube, or streaming, Maybe you see those ads because you play WoW or other mmos. I haven't heard any streamers talking about it, no articles or memes outside of dedicated communities.
I'm not saying those things dont exist. I'm just saying, as a general consumer of gaming media, it really doesn't come up nearly as often as it used to. It's more niche now, less mainstream. Which, unfortunately, means the player base is less dynamic.
Look you can go to the WoW, FFXIV, ESO, and OSRS subreddits or search for them on Twitter and see that the communities are still extremely active for these games. WoW has 75k on Twitch right now and MMOs are awful stream games. If you don't use mainstream platforms you're not getting an accurate read on what the mainstream opinions are.