once upon time there used to be a blues band called black sabbath. But they tuned down to C# started using hella distorsion for that and applied basic theory aka the blues scale aka pentatonic with a flat five into it, and that is how they wrote most of their songs.
and you know fag, sometimes you just have to let go. if you follow music theory to write all your shit it will get boring and gay even if you use the most obscure mode ever. You need to let go. that is what metal is about, not giving a fuck. Metal is about a rebelious attitude that can come in many forms, of either studying music theory, doing classical ear training through singing and practicing sextuplets with a metronome at 10000000bpm, or by picking up the guitar and beating the fuck out of the low E string, or B string (low 7th string), or in both forms.
I like how you picked this sacrament for a song, which is a little simplistic if you take elitist theory cunt classification of that is hard or easy. Why don't you try PoE title track middle section which is heavy and not that theoretical and a little more technical, or what about ambivalent, or TGE, bittersweet feast songs which are more difficult according to your elitist (not BM elitism) attitude.
Some of metal's greatest riffs are the easiest to play, and some of metal's great riffs are hard to play, and some are brutal to send your CoB loving faggot ass in despair (i know i'm gonna get shit for this, but sepultura's arise, or anything necrophagist, or suffocation and cryptopsy)
