I'm an artist that draws every same face ever in all my characters, but I still can make them distinct enough, I will show you how.
You see, OP, all these girls have the same face shape. None of them have a distinct face shape.
So how do they look different?
You can make any eye design from ANY shape. I'm not kidding.
More cat-eye shaped girlies will have a more "fierce" look than a character with downturned eyes or round eyes for example.
This character of mine ^ even has rounded eyelashes instead of pointy ones.
This character of mine has very square-y eyes ^
This one her eyes are literally a paralelogram? I don't even know how to describe her eye shape...
These girls up here have dinstinct EYELASHES instead of shapes, so when the shape ideas end, you can differentiate them by drawing crazy eyelashes.
and look at this dog girl, she has the saddest eyes to ever exist...... (they are very downwards and have a big droop)
So, there it is, the secret to avoid same-face syndrome. Different eyes.
Also OP, do not listen to "same-face-syndrome" people, they usually engage in cringe culture and most of the time don't give GOOD tips to other people, just know how to criticize them. I remember those guys being very loud around 2017 around the animation meme community even. I have seen everything, trust your sister!