I really don't think people understand the scale of youtube.
Regarding the scope, they can already discard a tremendously huge chunk of videos that simply don't get enough views to matter, or that idle about with very few impressions per week. They can hire those hypothetical 1800 people to just go after trending, highly active videos. That alone would help tremendously.
They can also programmatically harvest the referrer header from visitors and check if any social media sites in that data set contain certain keywords, or if the related social media and YouTube accounts have already scored badly from previous offenses. Or if any of the news and debunk sites are linking to the video while using certain keywords.
That's like the most basic of basic bots. Comparatively easy to code and deploy. Yet it would help highlight likely candidates in a hurry.
(I'm pretty sure they already do some variation of the above to avoid view count fuckery and the like.)
Again, if YouTube had acted early enough, they'd already have a flexible, home-grown, highly adapted system in place. They didn't, so now everybody will have to suffer while they hack together some gruesome Frankenstein monster that will deliver a huge amount of false positives and overlook an egregious amount of genuine offenders. That's entirely on them, and they deserve every bit of backlash that they will get from this. Does it suck? Yes. It's still better than pretending that it cannot be done, ever.
And about the overstepping of boundaries wrt ads, come on, we already have incredibly detailed Adsense (etc) controls that allow advertisers to specify exactly who they want their ads to be shown to. This is already happening. Big time. No, it doesn't make it OK, but it means this is a rather silly complaint. Obviously it's gonna happen even more, even regardless of this particular matter. However, it's another issue entirely, and would be much better addressed as part of that distinct problem.