[marcus_holmes]

If the requirements change, then so must the code. The code you wrote for phase 1 cannot (by definition) include the changes needed for phase 2. Especially because you don't discover the changes needed for phase 2 until partway through phase 1.

Writing code so that it can be easily changed to conform to new requirements is a trade-off, like everything. You will incur some cost to do this, probably longer dev times. In many cases this trade-off is not worth it.

And in my experience, shipping a new feature faster is always the goal. Dealing with the tech debt incurred is a tomorrow problem, and tomorrow we will have more funding/staff/time to deal with it than we do today. It's not always true, of course, but that's the attitude generally.