I've watched every episode from the start and some twice. I haven't found it sentimental, it's gritty. As well as all the issues Isambard mentioned - the "many other things", there have been two episodes focussing on male homosexual characters at a time when it was illegal to be so and two of the nurses are lesbian. People with mental illnesses and some with mental impairment (learning difficulties), are shown and how society dealt with that. Fall out from the workhouse era. Racism of course.
My mother-in-law was a young district midwife at the time some of this programme is set, shared a house with other midwives and worked with a few nuns. She was in a deprived area (not Poplar), and tells me how realistic it all is. Earlier on the character of Jenny Lee, played by Verity Lambert, reminded me very much of her when she was young from what I have seen in photographs and the voice of Vanessa Redgrave, who is 'Jenny Lee' as an elderly person, sounds like she does now!
I never tire of the programme & have read the books by Jennifer Worth on which it is based.