Yeah, I mean there's a lot lacking in he endings, but the thing I keep going back to is just how dangerous and insidious a technology the Reapers are. Not only do they just flat out kill trillions, but they first remove your free will, then slowly convert you into a monster.
Control is an insane ending, because even if you accept the premise that Shepard is pure and can do no harm, absolute power corrupts absolutely, so eventually Shepard in some form will be corrupted and create a new nightmare. Either that or it just turns you into the Borg, not a good way to go.
Synthesis is also a no go. Converting all life in the galaxy into some sort of organic/tech mixture could have millions of unforeseen consequences that you have no time to consider in such a short amount of time. Also, it does seem pretty ridiculous, to say "We must save the galaxy from the machines!" then have it be "We must all become machines!"
Destroy works because you also defeat the ultimate enemy, The Starbrat created by Leviathan that started this whole mess. The Starbrat is the soulless mass murderer or trillions and is completely unrepentant. It along with everything it did, needed to be destroyed. The fact that it could consider everything it had done a "solution" proves that it was so fundamentally flawed it would never come up with a proper solution. Destroy the reapers, destroy the starbrat. Play the Citadel DLC afterwards so that EDI and the Geth survive so that its not an awful ending to an amazing trilogy.