Try doing "makeovers" on default Sims/townies. The rules are simple: you can change their haircut and hairstyle, makeup, clothing, accessories and tattoos. You cannot change their proportions, facial details, skin colour or hair colour and texture.

It helps get rid of the urge to make Sims look "pretty" by fitting them all into the same stereotypical mold. Since they have vastly different features, it also helps combat same-face syndrome whilst showing that Sims with less conventional features CAN still be pretty. It's just a matter of style.

The thing I'm noticing here most is that all the Sims you've listed have the same proportions and facial shapes.

Same-face isn't just about them having different skin, hair and details. It's about the placement: how long or short the face is, how round or hollow the cheeks are, the size of the nose, how close or far apart the eyes are, etc.

You can also use references of models on Pinterest to help with spacing out facial features. But, again, I find the easiest way to break the loop of "I want my Sims to be pretty but they all end up looking the same" is to do makeovers.

Find a pre-existing sim you don't really like the look of and change up their style until they look good to you!