It was the ultimate sacriface though. In controll Shepard becomes the catylis but in synthesis he is uterly killed or deconstructed or something. I built my Shepard from ME1 and now I sacrificed him not for an easy way out or to let others continue the fight but for non-logical "hope". In fact it is just as possible for the Catylist to have an I told you so from the grave with destroy because some species might make an AI that will wipe out organics in the future. I mean people in real life are looking into reviveing giant carnivorous lizard! We are stupid creatures at our core to want or try such a thing.
The Ultimate Sacrifice for what though? That's the problem. Shepard doesn't become the Catalyst in control, but rather controls the Catalyst as well as the reapers. At least with Control though, it is suggested that Shepard would determine the fate of the galaxy because of his dominance over the reapers.
The galaxy didn't end before the Catalyst existed. The Leviathans created the Catalyst as a way of cementing their control and dominance over the galaxy. Their own short-sighted ambitions led to their own downfall and betrayal by their own technology. Whether the Catalyst existed or not, the galaxy would go on.
So your argument for Synthesis is "non-logical 'hope'"? That's a rather big leap of faith you are taking there, friend... I personally wouldn't want to gamble the fate of the galaxy and all living things on the prospect of hoping things would work out. Destroy isn't perfect and it certainly comes at a cost, but at least we know the reapers are dead and the Catalyst is gone with them.
Everybody should have known this trilogy was going to end with the ultimate moral dilemma. I "Destroyed" not only because I felt it was the right decision, but all of my crew, friends, and everybody in the galaxy (including synthetics) wanted to destroy the reapers and bring an end to the galactic destruction forever. We all knew there would be a cost. That doesn't mean we should shy away from it.