To quote glorious comrade Plinkett,
"don't any of you [redacted by ISB] tell me it was explained more in the novelization or some Star Wars book. What matters is the movies. I ain't never read one them Star Wars books, or any books in general for that matter, and I ain't about to start."
We're all free to pick and choose, I dinnae like the EU stuff in general and the notion I have to read that to be included in the discussion is kinda... you know, bordering on elitist. And now it's legends, glory to the vermin overlord!
That said, I don't dismiss the EU entirely because, as we've seen, it's still a good point of reference and focusing lens to approach new avenues of expansion into the post-Lucas era. It's helpful so long as it comes with the notice: subject to change without notification. Because you can absolutely talk seriously about a fictional universe, even if it's regarding things such as historical parallels, influences, social commentary, and literary merit.
On a side note, I like the whole First Order bent for their 'recruitment'. More over, I like that it was explicitly explained on screen. It's delightfully topical and puts me in mind of the formation of the janissaries.