Zhukov said:
No.
a) "Organics vs synthetics" was arguably a present theme, but the inevitable destruction of organics by their own synthetics was most certainly not. It was made abundantly clear in ME2 and most of ME3 that the organic-synthetic situation was not a simple case of us-vs-them and did not have one inevitable outcome.
b) The Geth were a secondary subplot to the Reapers threat. A subplot that was entirely resolved in ME3. In fact, that resolution potentially makes the Catalyst's bullshit even more nonsensical. You do not supplant the central conflict with an already resolved subplot in the final ten minutes of a story.
c) "Being destroyed by reaching too far"? That's not relevant to the catalyst space-child garbage.
A). Even if the current cycle wouldn't end in destruction, the Reapers had already mobilized and begun their cleansing. They couldn't be called off, regardless of how much evidence Shepard had to convince them otherwise. The Star Child says as much. Thats why he gives you the big choice: Dominate the Reapers at the cost of your own life, wipe them out at the cost of synthetics, or merge the two with unknown consequences. If you played a Paragon Shep who spared the Geth because "Synths are people too!", then destroying the Reapers would be hypocritical. You'd be wiping out an ancient sentient race because they threatened you; aka exactly what the Star Child was talking about. Synths and Organics work on entirely different levels.
B.) They are a subplot, but indicative of a much larger whole. EDI is part of it too; that the AIs in Mass Effect are beginning to gain true sentience. Its all foreshadowing to the revelation that the Reapers are also sentient beings, and the moral question of "is it ok to genocide them just because we are fighting? Especially if there is another option? What if they can be persuaded to be good, like the Geth or EDI?"
C.) It's exactly what the Star Child is talking about. Every cycle has it's examples of civilizations who grasp too far with technology and end up shooting themselves in the foot. It's in the nature of organics to keep pushing like that. The inevitable Synth war is simply the climax of these actions, which is what the Reapers are trying to prevent by blasting all galactic civilization back to the stone age. The Quarians, Krogan, Salarians, and even Humans are all examples of civilizations who have gone hog wild with their tech and caused galatic level crisis as a result. Can any of them be trusted with sentient AI?