Video needs synchronised captions, audio-only content needs a transcript, and visuals that carry meaning need audio description. Auto-captions alone are not enough.
WCAG 1.2.2 — Captions (Prerecorded) Level A
WCAG 1.2.3 — Audio Description or Media Alternative (Prerecorded) Level A
WCAG 1.2.1 — Audio-only and Video-only (Prerecorded) Level A
MDN — : The Embed Text Track element