There used to be a setting in Settings > Media to allow auto-embedding of YouTube videos.
If that was selected, then all you needed to do was add a YouTube link to a post and it would appear embedded. No embed code or 3rd-party plugin was needed.
I notice that my YouTube links are still correctly showing up as embedded. But that setting seems to have disappeared.
Is it now gone and just standard? Or has it moved to a different settings location?