Earlier quoted context omitted.
I've never been burnt out(yet). What does it feel like?
Imagine depression, but about your job. You try to force yourself to do the necessary tasks, and it takes enormous effort (if done at all). You may just no longer care. Feeling exhausted constantly, both physically and/or emotionally is also frequently experienced.
Burnout for me feels like the third day of that all the time. A fatigue so deep it's almost an ache. The thought of booting up your IDE feels like the equivalent of sitting through a lecture after that third day of little to no sleep. Sure, you can do it, but it just seems like such a chore.
That's burnout. It takes the things that invigorate you and turns them into chores. Then it breaks both your legs. Have fun getting your chores done.