I watched this with my elderly relatives, both of them absolutely loved it. I enjoyed it too, but I understand why it may not be everyone's cup of tea.
There were moments where it was light, humorous, and bittersweet. There were moments where it was deep, profound, and true-to-life. The acting from Jennifer Saunders, Ball Gilly, Judi Dench, Derek Jacobi, and David Bradley was very good, with all of their characters having personas that I found funny, charming, and moving.
The movie on whole was very emotional, with much of it being very moving and profound, and other parts being downright sad, and could be seen as "depressing" by some viewers. Sad films can be very difficult to judge as some will be "touched" and "moved" and think it's beautiful and wonderful and very good. Others will call it "depressing".
There was a twist at the end which was quite abrupt but I personally thought that the abrupt ending could be very true-to-life and you could even relate to Saunders' character a little bit. For me the abrupt ending was true-to-life, quenching, and real. However, I can understand why others would think of it to "ruin" the film entirely. It just shows what really goes on in the world, some like that displayed in a film, some don't.
Overall, I thought the acting, story, characters, and message of the whole film was truly wonderful, but, as all films go, it's not for everyone.