Another approach is to use NRaas Traveler to move some of the sims to a new world, thus keeping both worlds in play within the same game and having the ability to travel and move sims between them. Family and other relationships across the worlds will be preserved this way. Even if they never intend to play the current world again and would be using it as a source of visitors (for a while) and sims to pull into the new world using MasterController, many players find this way to be satisfactory as well. The currently under-performing world should not drag down play in the new one because only one world can be simulated at a time.
For long-running multi-generational play, many of us find that NRaas Overwatch and ErrorTrap (plus Register, Traffic, and to an extent GoHere) are indispensable to keep things running smoothly.
Without the mods, much of this is not possible because in that case moving to a new world means essentially starting over (in many ways).