Not in my experience. If you are agile, you can fix the architecture as needed. You end up with poorly architected code by deciding to continue building on top

Not in my experience. If you are agile, you can fix the architecture as needed. You end up with poorly architected code by deciding to continue building on top of something when it is no longer suited to purpose. That can also happen as a result of big investments in planning. That investment makes it very hard to rationalize architecture changes when the requirements change mid project. Which they very often do. No amount of planning protects you from the unpredictable.