I agree with OP and most of the posts in this thread. The Sims 4 is the one game in the franchise that has very little threat of failure and it's failure that causes drama and emulates to that downward spiral that most of us go through at some point in our lives. Sometimes you just have a bad day, but these Sims are so quick to cheer up that it's almost impossible to have a string of bad events as a result of poor decisions without willfully making it that way and you have to try pretty hard at that.
The element of surprise doesn't really exist because emotions are so controlled by the mechanics to favor positivity that everything just "rights" itself again to be in that dull, excessively pleasant, 'everything is always okay' state. The Sims are always autonomously seeking superficial activities, empty conversations with strangers and the same habits over and over. You can set up a house with no tech, an easel, a bubble blower and a bookcase, and all Sims are going to either constantly grab books and leave them all over the house or play games on their phones. They're all going to react to their decor over and over again. They're all going to drink water and do the same idol animations. Their Traits still don't drive their behaviors. Some of the new ones do, but the old ones don't even seem to matter.
I feel like at least having personal preferences regarding other Sims that can cause personality clashes or connections and express what they want in friendships and partners would help to create more visible depth to their behaviors. Almost everything they do seems more object based and it's long, long overdue for them to react believably to each other.