That's why I prefer dynamically typed languages for web systems; they start with the rigth assumption about the ever-evolving nature of the project.

The inverse can be said: a statically typed language makes it easier to replace parts later, do automatic refactorings, etc., and know you got everything right.

Dynamic just let you have less ceremony (no type definitions) but forces you to keep this all in your head (you still don't want to pass the wrong type of thing to the wrong receiver) and doesn't give you any assurances.

With type inference and/or autocomplete, statically typed languages are faster to write and easier to get right than dynamic.