Not days necessarily, but I think quite a bit of time should be spent data modeling, yes. Before you’ve ever touched the keyboard, it’s very helpful to attempt to model the problem on paper or a whiteboard. You quickly find problems with your initial guess that way.

Notes / data / extra et. al columns are the worst, as a DBRE. People inevitably shove various shit into them over time instead of making an effort to properly fix past mistakes, and at some point, they practically contain their own table.