You are being absolute in what people are capable of when they are burned out, which I think is foolish because the feeling and level of burnout is subjective.
Overcoming burnout is looking at your situation from the outside in. What you described is clearly a downward spiral. Logically, wouldn’t it be better to write some words for a plan than no words? If you can procrastinate for 25 minutes while you are burned out, you can spend 25 minutes writing a plan, even if it’s one word a minute or one word every 5 minutes.
The key is to break down what you need to accomplish and how you will accomplish it in the smallest incremental steps possible. Once you have that list, it becomes less overwhelming to make progress. Don’t focus on completion, focus on making tiny incremental progress.