What I find helps is to regularly clean out the Unplayed Households in the Manage Worlds tab.
The game creates inordinate numbers of random homeless sims, and they're generally hideous. Every in-game week, I go through and delete all townies that my Played Sims have not interacted with, or have no interest in interacting with in the future. Not having to keep track of them can help to speed up your game's loading times and reduce lag.
In a 22 Gen save, I can only imagine that there's a lot going on in your Unplayed tab!
