A network is the one part of the estate that is never redesigned, only extended. Every site addition, acquisition, remote-work programme and vendor connection leaves a layer behind, and each layer was reasonable at the time. What accumulates is not a design but a sediment, and the person who could read the whole thing has usually moved on.
The practical consequence is diagnostic time. When something is slow, and it is almost always "slow" rather than "down", nobody can see the path. The application team says the network, the network team says the application, and the truth is often a middle box nobody has looked at since it was installed. Meanwhile the business experiences it as the thing that makes everyone late.
Circuits are the other half. Contracts get signed for bandwidth sized against a traffic pattern that no longer exists, and they auto-renew because reviewing them requires an analysis nobody has time for. A meaningful share of wide-area spend in most organisations is paying for a topology that made sense before the applications moved.
Collaboration and contact centre are where the accumulation becomes customer-visible. The phone system predates the CRM, so the agent has two screens and retypes the caller’s details. Call flows encode a decision made by someone who left, and the reporting cannot answer why customers who abandon do so. None of it is broken enough to justify a project, and all of it is costing something that never appears on a line item.
Wireless is the most common single source of a bad reputation. It gets deployed from a floor plan rather than a survey, works during commissioning when the building is empty, and degrades the moment the space is used as intended, at which point the fix is presented as a capacity upgrade rather than a design error.