Disparaging? If so, I'll try to avoid it in this comment. Although I'd recommend you try to stick to that one yourself if you want others to reciprocate. You know, golden rule and all. (i.e. the following quote)
Fine, I'll play all the Blackjack you guys want except I get to choose what cards you get and what cards I get. We'll play all the chess you guys want except I get to choose your pieces and where they are on the board and the same for myself. No sense in starting with everything the same for all players. Otherwise, it wouldn't be strategy and tactics.
*sigh* Did you even read my comment? The strategy that happens before the game starts is
planning. If in your game your opponents somehow started with different resources, number of planets, fleet size, etc. then you would be completely right. However, they didn't. You got thumped because they had experience and planning going into that game. It happens to all of us at some point. My first MP I was happily researching trade ports when a "massive" (by my estimation) fleet phased in and killed me in no time. That was a little discouraging, but I'm better now and that doesn't happen so often. Occasionally, I'm even the one with the massive fleet (although to be honest, not very often), but I don't get it by cheating or stacking the deck: i get it by being better.
The only real complaint you have is that some players know maps more than others and, if I understand you, that friends play ffa together. These are very simple to fix, as has already been stated: play on random maps with locked teams. The only time the game actually gives any advantage at all to the host (other than the ability to play with their favorite settings) is if it's a map they designed themselves. This would indeed seem to be unfair, which is why I don't play custom maps I haven't seen before very often. I recommend you avoid them as well.
If you go into any game, not just sins, with no idea what you're doing, you will loose. That's not the fault of the game, or, really, even your fault. It's simply a matter of lack of experience. So don't give up, keep in there, pick your games more carefully, and I promise it will get better.