It seems to me that you should be directing some of your anger away from Celebrity and toward your travel agent who is not handling this well for you. First of all, the agent should have searched for good alternatives for you, and there are plenty out there. Secondly, if there were no acceptable substitutions for the land portion, the travel agent should be the one advocating with Celebrity to have you getting the correct refunds and/or assistance with bookings, flights by Celebrity, etc.
If one of Celebrity’s vendors, in this case whoever is operating the land portion of the cruisetour, oversold, the cruise portion would still remain intact. It should not have been difficult to find an option for the days you would be on land so you could continue to enjoy the cruise. Again, the travel agent hasn’t stepped up.