Functionally, GW doesn't know their own audience very well. Sure, their IPs are mainstream these days, but by and large, wargaming as a hobby is a niche that really only attracts a certain clientele who stand apart from the general public: the kind of people who, when given something new, can and will hyper-fixate on it to exhaustion. These are the kind of people who like difficult puzzles, the ability to test a system to its breaking point, and to come up with novel ways to play the game that its creators didn't anticipate.
In other words, these are the kinds of people you need to give a complex game system to in order to stave off boredom long enough for them to keep coming back for more. Otherwise, they're prone to losing interest and going off to find something else that's more worth their time and energy.
Unfortunately, this is a reality that GW either forgets or is unwilling to acknowledge when making corporate decisions that affect their games. "Simplified, not simple" indeed.
And that's before any talk about their "You can only play with what's in the box" and "if we don't sell the models, you don't get rules" policies.