Like other people said, having sims are different from your usual would definitely help. There are still plenty of careers and skills I have yet to try, even in base game. Try to pack your home lot with as many activities as possible so you don’t get bored staying at home. I also like to play stories, or at least write a short bio in my notes so that I become more attached to my sims. If you like legacy gameplay, try plum tree which doesn’t cull like the in game family tree and helps motivate me to play.
In general, think about interesting events in your own life: holidays, birthdays, graduations, weddings, vacations, even just family/friend outings, and incorporate those into your sims’ life.
I also find that having more sims makes the game more interesting, so maybe start with a family, pets, and established relationships instead of starting at square one every time.
