Most of the players in the top alliances have played together for years...I know because I recognize many of the names from 2013. They pretty much move from world to world in premade alliances, and begin with a huge advantage over the newcomers & uninitiated to Grepolis. They'll let you build your city up to around 5k or so, & then move in on you with their members in a joint attack, take your city, and gift it to one of their friends within the alliance. This is a cutthroat game, not about how good you are, but more so about who you know.
As long as who you know is paying to win. It doesn't help to know a lot of free to play players. I never pregroup, and have been parts of major alliances as well as new player alliances. I like being in new player alliances because otherwise the game is too easy, but it is a headache to get new players to communicate and work together. The honest truth is this game is incredibly pay to win. A lot of players who have been playing for years are terrible at the game. The last time I played seriously I had a single city on a hostile island that was almost all one major alliance, and one memorable night, I cleared every single one of their cities, racking up a huge bp count, catching myth nukes, LS fleets and CS's in harbors completely unprotected "because walls are for noobs". Then they counter attacked and ran into my Cerberus defense behind a maxed wall. Now eventually, they took that city from me, but it took them weeks, and I actually took a city from them on that island before they pried me off.
Anyways story time aside. You are not going to win against premade alliances in the long run unless you are in a premade alliance. Not because they are good players, but because they tend to be active, spend real money, and communicate reasonably well. I mean, in the above case where I took a city from the enemy, I had someone lined up to hand it off to immediately, only, somehow he used the CS for another city after saying he was ready to go, then had to get another slot, and build another CS, and I lost that city before he was ready to go again. It is that kind of poor teamwork that gets ironed out in premade alliances. People still suck at the game individually, but they can at least work together.