Sounds great, I'm all for it.

Sure the truth can be complicated, but I fail to see how implementing software that auto-links to a relevant article on Wikipedia causes Google to be the arbiter of truth.

Even if Google thinks climate change isn't man-made and links to sources backing that up?

There aren't sources backing up that climate change isn't real. That's a hill I'll happily die on. There are plenty of alternative sources which make that claim, but Google does not aggregate facts from them for presentation to its users. Because they don't have evidence.

Like I've said elsewhere in this thread, this isn't a revolutionary idea. Google does it on its search engine and the sky hasn't fallen. I remain unconvinced it would fail if they pushed it out to YouTube.

Note the solution I posed is something which Google already does on its search engine without calamity. Therefore I don't see a reason why it would fail for YouTube. In contrast the example you're giving seems pretty hard to just link to an authoritative source.

Put another way, I'm not advocating for Google to arbitrate the truth on a case by case basis. I'm advocating for Google to identify ahead of time which sources are well-researched and trustworthy, then outsource its fact-linking system to those sources.

If Google were to supply facts on a case by case basis that would be suspect. But that's not how the company operates, so I'm deeply skeptical they would become some kind of arbiter of truth.