I'm 46 so they weren't around when I was a child. My DD read quite a lot of them & I read them too, but there's many I haven't read.
I liked the Hetty Feather ones. I did not like most of the others.
I disagree that they are well-written. I think she recycles plot lines, and the writing is tired and cliched.
Some of her storylines are brutal, not in the way of telling a story honestly to children (which is how she always portrays it) but just sensationalist writing that I think breaks the contract with the reader & is both implausible & shocking.
There's an awful one where a child in a family is distressed, jumps out a window and dies; the story continues with the guilt felt by the parents at their treatment of child, at the very end she does a brisk chapter where it's all wrapped up, everyone is happy now. It was so trite.
If you are going to deal with serious issues, invest truthfully in the storyline & the characters.
I know she's very much loved, just not by me.
In every interview she talks about her unhappy childhood & how her parents treated her badly. It sounds very sad. But I feel it has overly permeated all her writing
I do accept there are many many books of hers I haven't read, however!