User blog comment:LostInRiverview/The Sims Wiki Monthly Question - May 2014/@comment-1997588-20140507142315

Personally, I think the game should be difficult, but not to the level that can make a player frustrated. The game should keep the casual everyday life elements, such as earning money, tending needs, and having a social life; all the stuff needed for survival. However, some challenging aspects should not be omitted entirely. Doing the casual everyday life for survival with no objectives to advance is boring.

The game should provide some objectives that pose challenges for non-casual gamers as well. The lifetime wish, skill challenges, and opportunities in The Sims 3 are good examples for this. Basically, skill challenges make you think that maximizing a skill isn't the only thing that's the most important. You might reach the top, but you might not earn 'em all! Puzzles, achievements, and unlockables are also good examples, for example the crash site in Oasis Landing, the hidden islands in Isla Paradiso, and the Simport unlockables (though this one is implemented in a pretty lame way).

However, even with all those challenges and quests, The Sims series is a sandbox game, and this aspect should not be forgotten. Making an entirely goal-based expansion pack, like World Adventures, makes the series lose its aspect. Don't get me wrong, I love World Adventures, and basically it's one of my favorite EPs, but this goal-based element is too strong and makes the game feel like not The Sims anymore. When solving puzzles is your aim, tending needs (and survival) is not what you're focusing anymore.