Domination of worlds by alliances and players who have already defeated the fortress.

Unfortunately I very strongly disagree with you on this. This game, whether by design or default, whether for good or evil, does not have a beginning and end. There is no end to the game or to the worlds.

The problem is however made less competitive once the first few alliances have killed the fortress because it has no end.

What is needed, and it has been said many times, is something that is after the fall of the fortress for players. Many don't want to 'waste' their investment of time and real money on starting a new world, sometimes with new rulesets.