It's really great that you liked this film (not being sarcastic) because it proves how subjective the experience of film really is. I went in with high-ish expectations, although after I looked a little closer after my viewing, I realized how many of the reviews were actually lukewarm.
As the credits started rolling, the guy behind me said (quite audibly) to his significant other, "so what." That kind of sums it up for me too. The whole 88 minutes are very enigmatic, but superficial. Filmmakers have gone to the Nazi/holocaust well so many times that it is difficult to imagine seeing something we have not seen several times before - thematically or emotionally. (Lore (2013) is probably the last film I have seen that covered that time and place in a relatively new way.) As it turns out, the filmmakers here - while very interested in dense visual atmosphere, aspect ratios, still photograph-like cinematography, etc. - are not that interested in delving too deeply into anything substantive.
Now, they could have taken a subplot like the history with the family that eventually took over the home of Ida's family and explored something nuanced about the limits of mercy and self-preservation. But the film saunters around this aspect like all of its themes, and I found the handling of that episode to be frustratingly inert.
I say frustrating because a lot of the scant 88 minutes is spent gazing at characters who are saying/doing so little. Quiet films (in terms of and action) can be effective; but you need to give the viewer something else. What we get, for the most part, is brooding in a bar, brooding in a car, brooding in a hospital, brooding in a nunnery, brooding post coitus, etc. I mean, at that point in the film, am I the only one who didn't see Ida's aunt jumping out the window coming?
And although I don't blame the actress who played the title character (given what she has to work with in terms of a script/direction), I have yet to see a more catatonic performance this year. The fact that she conveys virtually no personality - from beginning to end - kind of sucks the life out of any attempt at a character arc or change in identity.
With no real sense of emotional complexity, by the time I got to the deliberately vague ending, I just didn't care.