I'm not the biggest fan of the ending, but it did make sense in my opinion. The Reapers were the greatest threat to any organic life in the history of the universe, so sacrifices had to be made in order to defeat them. It sucks, but in this case they had to sacrifice thousands, maybe millions or trillions of lives, but also the ability to travel in between star clusters. Now what really made me angry is that there is a single ending which shows Shepard surviving the explosion of the Citadel, but of course to get enough EMS to even get this ending, you have to do multiplayer, as well as choosing what I think is the worst choice of the three; destruction.