There are quite a few things I haven’t done in Sims 4!
Things I’d like to do but haven’t done yet: have a vet business, have a Sim born with the Ancient Bloodline trait (I have two saves where I have toddlers with the Strong Bloodline trait, so I’m getting there), go to Forgotten Grotto, have an alien in the family/play as an alien, have a Sim learn all the recipes in San Myshuno (I have a lot of chef Sims!), investigate the wellness/herbalism/robotics skill more… gosh, there are loads. I also haven’t played as a premade or had one of my Sims marry one. I’ve not had a Sim live in Del Sol Valley or Evergreen Harbour.
Things I’ve only done once/with one Sim: go to Sixam, turn into a merman, become a Global Superstar, had kittens in-game.
I haven’t uploaded anything to the public Gallery (ie shared it), but I have built a few lots and saved them to my personal Gallery.