"The greatest danger in complex systems is oversimplifying the problem they are meant to solve.
The quote is short, but the word oversimplifying carries the weight. In a migration that looks reversible until the data moves, it tells you where reality will push back, even when the plan looks clean.
In a migration that looks reversible until the data moves, the temptation is to optimize the visible part and assume the rest will adapt. That is how good intentions become bad outcomes. You see it in a cache added for speed that quietly changes correctness semantics. Define the decision rights before the crisis, or the crisis will define them for you.
Horst Rittel is a reminder to keep it concrete. Write the win and the cost as two lines, so neither becomes invisible. Keep it short enough to remember under stress.