Here's my ramble on the theme, though:
Synthetics Versus Organics, to my mind, isn't the base theme in the series. The base theme is stated in the first game, which in further games seems to be the default state of mind for the galaxy's ruling class itself, though said by Shepard to Avina:
"You needed the krogan to stop the rachni. You needed the turians to stop the krogan. Who's going to stop the turians?"
The asari hold back information they have from the Protheans while the Reapers are invading, and hold back support from the Alliance in the expectation that their advantage over the galaxies' other races will be more important to preserve than the other races. Their planet falls because of this mindset.
The salarian dalatrass warns Shepard of the 'inevitability' of another krogan war, if the genophage is cured. The salarians have plans to
uplift the yahg either to counter this or
because...Han'Gerrel will press at any advantage to kill the geth, up until the warning of utter annihilation presented by Shepard (if it's sufficient), because he knows it's inevitable that the geth will kill them if they have the chance. When he ceases fire, peace occurs. To the extent that a few geth get shot later on by quarians as a misunderstanding and don't shoot back, even. But it never occurs to anyone but Shepard and Tali that it could happen until it does.
The humans, as often happens in this kind of story, are mostly noble, except for probably the second-most powerful human stll alive, TIM, who wants to use this situation to grind the rest of the galaxy under his heel.
The turians are a borderline case, but I could see the concern that a turian-krogan alliance would become dominant in the galaxy, though I don't recall anyone expressing it. Odd that the most hostile race (to humans) in ME1 would be the most noble in actions, at least in presentation, but there you go.
Still,
this is presented well.
This theme is recurring throughout the series.
This theme fits the ending spiel best, even. The cycle is a combination of
Summon Bigger Fish and this, that the Creator will always conflict with the Created.
Where it falls apart is where the Guardian never got rebelled against. That really needed to be the reason for the Crucible in the first place, that Harbinger locked the Guardian out of the cycle some millenia ago for its own purposes. Having a boss battle against a Harbinger avatar would fit here as well, making him be the one who stands in the way of peace... but I still see the possibility of, well, saving this ending as is, if they throw more of that into the exposition.