Originally Posted by Hikaratu
The difference between this and your magic the gathering anology is the team element, if you play multiple deck games with alliances in place you can blame your teammate for the loss if it was obviously due to his poor deck construction or bad use of interrupts etc etc, as that's how it went down. I probably just rambled on and said the exact same thing in all of these paragraphs but w/e, people will get the picture skimming over.
The analogy still works. In MTG, you have no control over luck, so saying "oh, I lost because I got mana-screwed" or "oh, I lost because he had a good hand" are two things that will comfort you, but you will never get better by saying them. There's always SOMETHING you actively could have done to play better, and if you think that you are perfect, then you are, well, wrong.
Similarly, saying "Oh, we lost because they were a premade", "we lost because [x player on our team] sucks" or "matchmaking is bugged" is not constructive. You cannot improve at all by saying those sorts of things, because those are factors outside of your control. The most constructive thing you can do is analyze what YOU did, and improve on that. A replay feature would help a lot with that. I know for sure that I make dozens of mistakes every game, and I want to see them all so I can improve.