How I Learned to Stop Worrying and Ignore WCAG

1.1.1 Non-text Content (A) Continued

Less "exceptions" and more slight variations of alternative text.

Controls, Inputs: should have NAMES instead
Time-based Media: text alternative doesn't need to serve an equivalent purpose; instead it just needs to provide a descriptive identification of the media. See Media-related Success Criteria for more information.
Test: If the alt text would invalidate the purpose of the test, then the text alternative should describe the purpose.
Sensory: If you have content that creates a specific sensory experience then alt text needs to provide a descriptive identification of the content.
CAPTCHA: alt text must say that its a CAPTCHA and alternative CAPTCHAS for different senses must be provided
Decoration, Formatting, Invisible: If the content is purely decorative, used for visual formatting, or not presented to users, it must be ignored by assistive technology.