It’s funny that you write this, as when I was at Salesforce, I picked up a nested list drag-and-drop task solo except-testing (as the “go to” UI person on the team), and it took me almost the entire release cycle (1/3rd year release schedule (but picked it up later into it)) to complete it. While it turned out good (and I remember the feature’s implementation getting praise by a senior manager at a sub-org demo meeting), that I was called into a team meeting for a “Root Cause Analysis” (paraphrasing) to discuss why the feature took so long to implement.