I live near the black forest and it has never gone away here. However it is eaten purely as a cake and not served as a dessert.
I'm not sure what used to be on restaurant menus back in the day as I left the UK in my early twenties, not having eaten out much. My father ate out a lot during the week as he was a "commercial traveller" and fed up with restaurant food and my mother was such a good cook we always ate at home. I am coming to England for a two week holiday soon, so I will be interested to see how fashions have changed. I expect lot of the stodgy puddings of yore will have vanished (won't miss them).
I am looking forward to lots of fresh 🐟 fish dishes and maybe trying some Indian food. And seeking out a good carvery - now that's something that didn't used to exist. So I'll be following this thread to see what people eat these days.