Adobe has done some remarable things in the area of editing and face recognition, but this is a very basic deficiency in data handling that I never expected from Adobe.
Apparently, "date taken" and "keywords" are not written back to the image metadata when changed in LR CC. This means that a user can spend an enormous amount of time entering corrections to dates (especally scanned photos and old videos) and additions of keywords (names, places, events, and categories) - only to lose that work when exporting or migrating to a new system - even to Lightroom Classic! Also, the link to SmugMug does not work properly because "date taken" will be missing so it will not display and will not sort properly.
I am one who is now in a quandry because of all the work I have put in that may have to be done over. I feel the need to warn any potential Lightroom CC user that it is a dead-end system from which you can never retrieve your data. I earnestly hope that your developers can see that this is a critical problem, and it has a relitavely simple solution. Like Adobe Elements Organizer, you can simply write dates and keywords back to the metadata of the image files in an option. PLEASE, save this old man from months of repetative work! Thank you for your consideration.