Accessibility is important and should be a part of a regular WordPress development process like responsiveness and performance, etc.

You should always check if:

• Users can navigate using keyboard only
• Users can navigate using VoiceOver
• All necessary images have alt text
• All links have text and are correctly linked
• Color contrast is sufficient (using the Color Contrast Analyzer or Lighthouse).
• Videos have captions
• etc.

For more information, check the official WordPress a11y guidelines and Infinum's Accessibility Handbook.