This is standard PRINCE project management skills and what is most surprising is that we had to forget it and go focus on agile to remember the value of it. If

This is standard PRINCE project management skills and what is most surprising is that we had to forget it and go focus on agile to remember the value of it. If one has tasks that are fully independent, then one has no dependencies. Once you have dependencies (and almost everyone does) then you now have the capability for them to block other tasks, or to create slippage down the tree of dependencies. Recognising a critical path and ensuring that those tasks always have higher priority is why project management is not something that should be over-simplified.