Usually when agile approaches (kanban or scrum) fail it is because there's an unsolvable bottleneck. Typically too small team, lacking knowledge or skill for the scope, problematic environment (development or socially) or someone is pushing "done" work causing skyrocketing development debt that quickly comes to a head - typically a prototype remains in production, switching too early to maintenance mode for business reasons.

Waterfall cannot identify those risks without huge experience. Scrum tends to exacerbate some of them. Kanban with sufficient number of phases tends to expose the problem, but not necessarily fix it.