In my opinion, you have to go all the way back to 2004 with Dawn of War to get a good w40k game, and as Space Marines feature heavily in games since then, it’s a very nice change that SM aren’t front and centre.
Also, Deathwing was a flop. FS have done a good thing staying away from Space Marines and all the booming voice “With me Brother!” generic voice acting.
I think in fact that Games Workshop have some kind of weird self-fulfilling prohpecy about SM.
“Space Marines are the popular miniatures”
Launch more space Marine models making marines the vast majority of models you can buy
“No one is as interested in Xenos they’re all buying Marines!”
And so GW have an idea that because people are buying marines they launch more marines and assume people love marines. They put marines in everything hoping people will like it.
Some Eldar Models haven’t been updated in… years and years.