When millions of people are buying your product/platform, there are going to be groups with different needs. Career players being one of them. (FUT players make them the most money, of course, so they will get most of the resources, but something has changed.)
It seems to me like they have found it financially worthwhile to invest in keeping Career players around (or bringing them back to the game), and what I personally (and many others) have been crying out for, for years, is our own separate, more serious, far deeper, realism-based, knowledge-based gameplay. Having a Career Mode without that is like bolting a realistic transfer system onto Mario Strikers Charged. So... It's more than I ever expected.
Whether you can do enough to give Career players what they're looking for when you're working on the same code base as everyone else, and don't have the full team working on it, remains to be seen. But I do think the intent is there. "Sim mode" is potentially the most significant addition to the game since sliders, IMO (and I'd love to say the same about FC IQ but I don't see the point in it if the AI is still not allowed to actually do anything, i.e. defend).