If you have a lot of or all of the packs, try going back and revisiting some of the older ones. I found when I was getting bored that I had forgotten stuff from the older packs (and I mean big features, like the entire retail system or clubs system). So maybe going back and trying something that you haven't done in a while, or something different altogether.
Also, I find doing challenges fun and helpful to get out of a rut too. Personally I like having a goal to work towards and get bored when things become too easy or lack direction. At the moment I'm doing my own take on the Build Newcrest challenge where I have to rebuild all the worlds, not just Newcrest, and I've set goals for each generation to fulfill an aspiration as well as some other things related to that aspiration (and of course, building something). I find there's enough to do in each generation that I'm always working towards something, but it's also not unachievable.
Another thing you could do is focus on the sims whims for a while. Sometimes they can take your game in directions you hadn't really planned on and make things a bit more interesting again.