One sign of burnout is contempt for your audience. When you get too cynical, it's time to quit.
When art tries to get political (usually lefties do this) it gets soul-crushing and boring in a hurry.
That is because true art is based on inspiration—and that comes from places where there are no politics.
Audiences (viewers, readers) can sense the fakery in a hurry even if they can’t verbalize it.