Having played several worlds, and one of them in a pre-made, I feel that I can share my thoughts on them.
Pre-mades are always going to be with us, I am afraid, the faster/decent settings worlds especially. Why? Because they are rarer. which means if a bunch of players want to get into it who all know each other and they wish to play decent settings, they have a very limited selection to pick from. And this inevitably leads to them joining together and fighting together with one goal.
That said, the majority of pre-mades are usually going to fail. A few rise to the top and stay there, yes, but the vast majority collapse or split due to many leaders, not enough players. Or something else entirely, often they are aggressive and cause too many enemies.
I do not think they have 'broken' the game, but they definetly have ended the 'magic' of starting, except in slower worlds. They start, now, to win, and there are less worlds for them to start. Possibly the solution is to create more speed 3 worlds, no morale in order to encourage less pre-mades as there are more worlds for vets to play in. Instead of waiting months on end for a world and then 3-4 pre-made alliances join, releasing more worlds with the favoured settings in order to encourage vets into more worlds will see an increase in the activity level of new players and a drop in pre-mades and/or the desire to form them?