The solution for this is to not set a takeoff time. Without one set, SkyDemon always assumed you are about to take off.
I understand why the behaviour you're seeing can be frustrating, but we have taken a decision not to alter a saved route when loading it in any way, because it would be unacceptable to load a route, save it, and have it silently changed without your knowledge. We show a warning just to let the pilot know their takeoff date is set in the past.

when you load a flight plan from the cloud or your PC it would be really useful to have the take off date default to now plus an hour. I re-use my flight plans all the time and find this really annoying. At the moment it defaults to the time which was saved with the plan. For example

Save a flight plan from EGTF to EGJJ  with take off set on 1st January
Re-open from cloud on 1st July - the take off date is still set to 1st January