What is full stack web development?

The meaningful line inside a full-stack project is the API contract — the agreed shape of every request and response between the interface and the server. One person holding both ends means that contract is designed once and changed in a single commit, instead of being negotiated between two contractors who each have a version of it in their head.

The honest limitation is depth. A specialist who does nothing but iOS or nothing but database performance will go further in their own territory than a generalist will. Full stack is the right shape when the project is small enough for one person to hold entirely and the integration risk is higher than the specialisation risk, which covers most first products but not a large platform with a dedicated team per layer.