At least the garbage is pretty consistent, so I can pause the videa and tell my wife that the phrase X Y Z in the subtitles is actually A B. (The number of syllables is almost always correct, but often the number of words is not.)
On a side note, it's not YouTube, and it's translation instead of strait subtitling, but I've seen some pretty bad English subtitles for Netflix's La Casa de Papel (Money Heist). I don't know a lot of Spanish, but I do remember a few times the translations were very odd and I realized the translator was translating a person's surname from Spanish into its English meaning, and not capitalizing it. It would have been just fine leaving the name untranslated, as my wife and I could both clearly make out the names of the characters. I presume a human translator would know not to translate names. I hope the subtitles I saw were third-party subtitles where someone ran Spanish subtitles through Google Translate.
For the vast majority of people on this planet, English is not their first language (if they speak it al all), and their command of English may often not be good enough to comfortably understand all of the content they might want to enjoy. And it's still the case that most content on such platforms, and certainly often the most viral one, is in English.
And even beyond that, people sometimes learn other languages, in which case watching something in the target language with subtitles can be a very helpful step.
Oh and, the automatic subs are absolute trash if whoever is speaking is not doing so with an american accent, in a perfectly clear room.
If I want subtitles or translation I should be the one deciding, or at least give an option to opt-out, which isn't doing it every video. And that was for subtitles, because that wasn't possible with titles and descriptions.
Auto closed captions quality depend on the language and the locutor. It works well for "presentation" content like vlogs and news, it fails for casual discussion or songs.