Regarding the OP, who by the way has acknowledged on another thread that we don’t need to be battered with posts like this: I’d go one step further than Asbjörn Torvol has above, and say, if you want to be dogmatic, be dogmatic – but know that you’re making a choice.
You have the power in that situation – I have to drop this in right around here:
There’s a good case to be made sometimes for subjective synthesis – synthesising, wilfully creating, immersion in a belief system, to work to the maximum with one specific current, type of entity, or whatever.
I’ve experienced this myself when I worked with Ahriman and the influence was profound, I couldn’t stomach certain kinds of foods that were linked to Ahura Mazda, and I got great, life-changing results because of that, because I threw myself in 100% and didn’t try to “cheat” or look for loopholes.
And prior to that, in my RHP era, I threw myself 100% into that to the apex point of merger, which is what has become the foundation of my work with magick, and again I didn’t cheat, maybe eat a tuna sandwich, bet on a horse race, whatever, because I was totally dedicated at that time to getting the goal and I didn’t see any value in distractions.
Even on here, when I coach people through the core shamanic system, one of the biggest problems comes when people try to work in bits of other systems before they’ve even begun, which is understandable, and that system will rapidly adapt to more or less anything you want to syncretise it with – but at first, the only way to be certain of making the interface this provides is to do it exactly as written, and as taught to probably tens of thousands of people over the years.
If you’re making beef stew, make beef stew – don’t add sprinkles, sushi, and a handful of Lego bricks because you didn’t want the group “non-food items” to feel left out. 
But when you get really good at beef stew, you might decide that adding some dried apricot, or bacon, or whatever is going to enhance your recipe, and that’s a decision made from mastery, from deep immersive knowledge of what makes a really good beef stew.
A lot of people criticise wiccans because they will choose a god, and a goddess, from pretty much any pantheon and attach whatever attributes and modern values they think are great to these spirits, and in my own experience, firsthand and personal, of changing reality in my own life and for others through magick, I get that – you CAN often work successfully, even on the same project, with spirits from different pantheons, paradigms, and whose lore and legends seem to clash, but ONLY if you’ve already come to know them tolerably well, to the extent you can ask questions and receive information accurately.
Other times, probably not so much – they may be in opposition for a reason, because everything other than the formless Source has qualities, meaning it IS one thing and therefore is NOT another, and by the time you get to entities like gods and demons, those details are going to be complex enough that you may get harmonic clashes.
Harmonic clashes? Every key on a piano is capable of creating truly beautiful and inspiring music, but you can’t just mash a bunch of them together at random and assume the outcome will be anything other than cacophany.
This is because discord (which, again, also has its place in music when used with full understanding of the effect, as a counterpoint or emphasis against harmony) arises when certain frequencies are struck together at the same time – as a general rule, any two or more directly adjacent white notes on a piano/keyboard should never be sounded unless you’re aiming for a dissonant effect by choice.
(There’s a full explanation of this in music, with examples, here.)
Sometimes opposing things work well – but if you’re undertaking a serious project, you need mastery of the individual elements, which in magick means personal experience of working with the spirits somewhat “by the book” to begin with before you’ll know when to do the equivalent of adding black pepper to strawberries, or a squeeze of lemon to chicken chow mien.
To go back to the OP, and what I posted further up this thread, the JoS system is a choice, a whole current and system that people do get results from, but it’s not the whole of the truth.
If you want to insist all your demons show up looking like Chris Hemsworth (and there’s certainly nothing wrong with looking like that! amirite, ladies?) then go for it, but you’re also going to limit their opportunity to show up looking like muscular ram-headed gods in armour, or strangely maternal dark green three-headed snake Queens (love to beloved Buné there!).
And those aspects have lessons, and usefulness, and can teach us different ways to work with these spirits that would never otherwise appear if we insist they show up in anthropomorphic drag.
So yeah, choice – that’s the difference between a magician, and a religionist – a religionist gives over power to absolutes, which then bind his or her actions and eventually even dictate the things he or she may think about, clamping down tighter and tighter on free will; but the magician chooses what absolutes to use, for the experience or for a purpose, and then, when to abandon them in pursuit of his or her personal agenda.
But they never have mastery in their own right.
That just means a lot of people replied, it’s an automatic thing the software does.
