I agree with you. Its the most practical way to handle all of this. I think the extra percentage is a fair way to help offset the increased costs for some, is a nice bonus for others and yet still not enough to get some to ge
t the "same deal" on a comparable cruise at a later date.
If the OP wanted a more fair system the only thing I can come up with is only allowing people to book a very comparable cruise at the same rate tier as the original booking. So, say you booked a 7 night med cruise on platinum opening day for June of 2020, you would be allowed to book a 7 night med cruise in June of 2021 for platinum opening day rates (of the 2021 schedule), even if the current going rate were higher. This gets you to about as close to even as possible IMO. BUT there are a few issues. The first being what if there are no similar cruises being offered next year, then the customer must take a refund in order to be completly fair to Disney since some itineraries are much faster to book than others (meaning you could have had a lackluster 2020 cruise planned that was getting the axe because no one loved it and then rebook a *hot* itinerary). Another issue is that cruises tend to go up year to year so everyone would likely be paying at least a little more. A third issue is that circumstances will change for people between this year and next, people will graduate/ get married/ have babies/ not be available, so that what the customer needs in terms of the cruise may change. There is limited flexibility with this plan. There is also the logistical headache of matching up the booking tiers.
You could say combine the two methods,
DCL gives the 125% good on any future cruise but make booking rates the same tier as the initial booking rate. I dont believe this is fair to Disney in several ways though. I think DCL (and most cruise lines) is doing something that is a good compromise of whats best for both them and the customer and also what is somewhat easier and makes most people happy enough to stay with DCL.