@azelira There is no way to selectively disable packs, sorry. The pack selector is an Origin/Windows thing, and the utility that does it is only for disc-based installs, again in Windows. (It works by moving files that don't exist in macOS.)
What you could try is just moving the folders for the packs you don't want to load. Since uninstalling a pack is as simple as deleting its folder, moving it to somewhere the game doesn't recognize should also work. I haven't tested this though: I've uninstalled a pack this way, with no consequences, but I didn't try to move the folder back later.
If you want to try, look for the Sims 3 Packs folder, either in Applications or Macintosh HD > Users > your username > Applications, remove a folder, load the game to make sure the pack isn't loading, then put the folder back and see what happens. Worst case scenario, you just need to redownload that one pack.
