I'd say that the needing rewrites is bad for the future clarity of the code. So much so that people conclude the 50% performance hit is worth it to use open polymorphism (interfaces, etc.) over closed (tagged unions, algebraic data types, etc.). So I optimize for the ability to reason about over the lifetime of the project above the current ability to reason and above performance (with exceptions).

What is adding a polygon going to do? Either back to the 'bad' interface to hide variable object size, extend to a tagged union with a size of the biggest datastructure - hurting cache performance each time it grows -, or an involved Object of Arrays structure - not good for clarity but great for performance.

All while having to remember which field, width or height, to use for the circles radius.