In the Twenty Nineteen theme, for example, when you specify a page as your site’s home page, WordPress automatically creates an alternative text using the page title.
The default WordPress theme comes with built-in accessibility-ready features.
Screen readers need alt text to help visually impaired or users with learning disabilities understand images included in the content.
Any inline images included in your theme should have alt text. This includes featured images. Even if the code is present to display alt attributes, however, appropriately crafted alternative text still needs to be input for those images.
Background images do not require an alt attribute. Purely decorative images like background images and other non-text content should be added via CSS so assistive technologies can ignore it.