Drupal 8 is more accessible out-of-the box than previous versions, but still lacks some useful features.

I had made my Drupal 7 Paragraphs based layouts as accessible as possible, and ported all of that over to 8.

I had more ideas, though, but held off on them in Drupal 7 since anything developed for 7 would have to be heavily rewritten to work in 8.

So, for us, Drupal 8 brought major accessibility improvements for our content creaters/editors.