You are right. She only plays one character in whatever she's in. She only has one facial expression, one delivery of her lines, one-dimensional characterizations. I don't think she ever had much training as an actor.

To me, she is an amazing actress. She so much becomes the character that she is portraying, that I forget I'm watching a movie, and I feel transported to that place and time that she is portraying.
She is also warm amd charismatic in her character.
This is as good as it gets.

I second the notion the other user suggested. Definitely check out her performance in "Fried Green Tomatoes". I hope that it changes this opinion you have about her if you haven't watched that movie already.

I've not seen her in many movies. But I have to say she was outstanding in Boys on the side.

A misguided uninformed opinion. She's totally different in everything she's in. Try watching her wonderful performance as the working class single parent in The Client, or her touching role as an aids victim in Boys on the Side or the beaten wife who escapes her violent husband in Fried Green Tomatoes.