A topic isn’t worth pursuing when it fails on any of four criteria: the SERP is locked by authority you cannot beat, there is no real demand, you cannot add information gain over what exists, or it is irrelevant to your goals and audience. Any one of these is enough to call the topic dead. The first is competitive: if the results are owned by sites whose authority and trust you have no realistic path to match, you can write the best page you can and still never reach the visibility that makes it worthwhile. Effort does not overcome a locked SERP.
The second criterion is demand. If almost no one searches the topic, even a top ranking returns almost nothing, so the page cannot earn back the work regardless of how well it ranks. The third is information gain: if everything useful has already been said and you cannot add a genuinely better, clearer, or more current angle, your page is one more copy in a crowded field with no reason to be preferred. The fourth is relevance. A topic that does not serve your goals or your audience may be winnable and in demand and still be the wrong thing to build, because it pulls effort and focus away from the work that actually advances you.
This rejects both the belief that every topic deserves a page and the habit of pursuing topics on hope. Naming a topic dead is not defeatism, it is a real and valuable decision that protects your time for the work that can pay. It ties directly to the portfolio kill rule: a healthy set of pages is shaped as much by what you decline to build as by what you create, because every page you do not write on a dead topic is capacity returned to a live one.
To decide, run the topic against the four criteria before you commit. Is the SERP beatable, is there real demand, can you add genuine gain, and does it serve your goals and audience? If it fails any of them, drop it and move the effort to a topic that can return. Kill on the criteria, not on hope.