Just do it now maybe works on small projects, but large projects that span multiple teams and stakeholders typically have enough little tasks to complete that “

Just do it now maybe works on small projects, but large projects that span multiple teams and stakeholders typically have enough little tasks to complete that “just do it” might be referring to 1 of 50 different things. You need some way to prioritize and work against those priorities, typically measuring impact or some variation of ROI.