[Aqueous]

Data structures being badly designed is a perfectly valid and common blocker. That is why we try to design things correctly, after all - to avoid blocking future engineers when they try to change the system. Badly designed data structures can make a system impossible to extend. Regardless of who is to blame, we need to call such things out so that people actually pay attention to data design in the future, and avoid things that are extremely costly but necessary to fix. So I'd say it is productive to point it out.