I'll grant that on previous occasions YouTube's auto captions have been hilariously wrong, but these days it really seems to be more fully baked.
I was curious to see how well the feature worked on older videos, and tested a random CS lecture from 2008.[2] Captions were perfectly fine.
The caption feature rolled out September 2009. [3]
[1] https://support.google.com/youtube/answer/6373554?hl=en
[2] https://www.youtube.com/watch?v=QMV45tHCYNI
[3] https://googleblog.blogspot.com/2009/11/automatic-captions-i...