I've resorted to resending booking confirmations from my email sent folder to Tripit, even past trips going back to 2016 and it seems to work fine, so far. I think Tripit will be the best alternative, I don't use these apps for travel planning anyway, only for itinerary management.

Tripit does not seem to work well if you change your itinerary and sent a new confirmation, it just adds the details to the existing trip and leaves the original flights, hotels etc there so you have duplicate hotels, cars etc and flights, so needs to be manually edited. Nor does it allow you to enter the name of the traveller for trips that you are following, at least I couldn't find anywhere to do this so added it as a note. It is also slower to process the email confirmation and add to your trips than TC which was almost instant. It doesn't recognise certain train operator confirmations but its not a big deal.

They're the main differences so far, will be interesting to see what I get when it gets close to departure date, I suspect nothing as you need to subscribe to get any flight alerts, gate numbers etc. So I'll use the airline app for that.