There are a lot of reasons. I was going to be sarcastic, but since you put some time into your post, I will try to give a decent marketing breakdown.
More than likely they are looking away from the expensive advertisements which you listed.
TV is expensive and in general TV viewership is down. Also the demographics which play WoW, or would Play WoW, dont necessarily line up with viewer demographics. So having to have a marketing department analyze show demographics, viewership, viewership retention and time of show. Then produce TV spot advertisements, which is also expensive.
Radio. Radio adds for a visual MMO experience would be a mute point. You would have to research again. Listening Demographics. Time Periods. Stations. Ect. Then produce a radio advertisement. And considering most people use Spotify, Pandora or other listening services. Which service do they advertise on? All? A few? That gets expensive, for something that will be ignored, skipped, or for people who pay for no advertisements, be nonexistant.
Movie Theatre Adds. Same problems as Television. Expensive. Market Research. In addition, theatre attendance is largely down. And for streaming services, again, which do you target? Whats your audience? All of those compile.
Now lets look at a huge chunk of where Blizzard is getting its advertisements. Streamers and Youtube Content Creators. There is a guild called Onlyfangs which has some of the most viewed streamers on twitch, all playing Classic Hardcore together in a parody guild for entertainment. Across all the streamers, you are talking 100k-200k Viewers every day, for hours.
Then add on other streamers playing WoW. Including Asmon. 50k-100k Viewers every day.
Then youtube. Bellular, T&E and others. Combined they get millions of views on their videos. Not to mention clips. Which also get hundreds of thousands of views.
All of this, while being income for the content creators, is free advertisement for Blizzard for WoW. Next to zero financial investment in producing this publicity. And on top of it being free, it all pretty much targets all of their demographics.
Then add on Twitter and other media. Very cost effective to produce. Gets hundreds of thousands, if not millions of views and shares. And many can be produced by current employees and developers, for free, by having it as a part of their job role.
So lets go back to the start. You have several means of traditional advertisement in forms of media, which are by and large declining, or difficult to zero in on demographics. In addition to the issues, they are quite expensive to advertise on, in addition to the expense of creating the advertisement.
Or you can have the advertisement be almost free, and rely on making good content for streaming and players.