Many mistakes move us forward more than backward. Conscientious people often experience a springboard effect following mistakes, whereby fixing the mistakes accelerates growth faster than if they'd never made any missteps.
Kantar's codebase was legacy old. The kind of technical debt that isn't a line item on a sprint board but a structural reality that shapes every decision the company makes. Rebuilding the architecture to support what I'd designed would have cost more than the organization was willing to invest, regardless of the Barilla deal sitting on the table.
Do you blame others for the choices you are making? Have you blamed others for the previous choices you have made? To shed more light on these questions, you might also ask yourself: "What am I responsible for, and what power do I have?" From there, you might agree with this self-reflective response: "I am responsible for, and I've got the power over what I think, do, say, learn, and choose" (Purje, 2014).