I can’t speak from experience, only observation.
GW put out a game called Inquisitor which was the closest thing to a 40K RPG they published directly. It was a 56mm game. It’s been a long time since it has been supported, but it has lived on in the community under the heading Inq28 (using 28mm). https://www.reddit.com/r/Inq28/comments/182y7xi/where_are_the_rules_for_the_inq28_game/ is probably a decent place to start looking for rulesets, and https://28-mag.com/ has a lot of adjacent content.
In GW’s current rulesets, Necromunda is probably their most narrativey campaign game. https://start-warhammer.com/necromunda/
If you want an actual RPG then C7 publishes two games. Imperium Maledictum and Wrath & Glory.
WarhammerTV is (a) cheap and (b) not GW’s main product.
The 9.99CAD is for WarhammerTV & Warhammer Vault & the exclusive miniature & unlimited army lists in the AoS/40k apps & a discount on merch.
The audience (i.e. people paying that money) is tiny compared to, say, Netflix.
So it isn’t bringing in a lot of money so GW isn’t motivated to spend a lot of money on making the app to view videos actually good.
They are a miniatures company who make most of their money from miniatures. They are keeping their focus there and most diversification is, I guess, usually one guy’s pet project rather than a major business move.