The destroy ending can be summed up by paraphrasing Fallout 3 a bit. "[The galaxy], with all its flaws, was deemed worthy of preservation."
You don't rape every culture in the galaxy with reaper tech on the word of the enemy general or submit Shep's mind to inevitably fall to the Reaper hivemind and start all this over again; because remember, literally no one we've seen that has jumped in to control or co-opt or otherwise partner with the Reapers has been anything but subsumed. Remember how for the entirety of all three games, we've been beaten broadside over and over with the idea that one of the Reapers' biggest and scariest powers is convincing people that LUDICROUSLY BAD ideas are in their best interest?
Also, no one should take starbrat at his word about inevitability. The one being who has personally ensured every cycle says that if you kill him and his forces, the cycle won't stop.
I also thought it was stupid that destroy hits "all synthetic life". Why not just say it hits everything with Reaper code since EDI, the Geth (if they survive) and...obviously everything on the Reaper side all have it? It sounds a bit less like important-sounding nonsense that way but that's just me.
But that's a side tangent. The point is that even if we DO fuck up with machines later on, that'll be on US. We're given the CHANCE not to, we're given the freedom to have the chaos of life, in whatever form it takes, to go on.
I personally ignore this stupidity altogether and just headcanon in my own ending and have Citadel as an epilogue, though. I suppose it's fun to talk about in a weird way, but when seriously coming down to it, I never will accept "Press button, save (or doom in one of two horrific ways) the galaxy" as a conclusion.