Then I think you're still missing the point of the comment you replied to. Chalking something up to "human error" is not a particularly useful conclusion to come to; it doesn't really solve or prevent any problems. The takeaway should be that a system did indeed fail from a design flaw. That system was not the space shuttle as a mechanical device. The system that failed and needed to be re-designed was the process of spacecraft engineering: NASA was lacking in structural incentives and protections necessary to ensure that predictable catastrophes would actually be predicted, and that such predictions would be communicated through the organization before anyone got killed.