YouTube advertising works a little differently to, say, Facebook. For advertisements longer than 30 seconds, the advertiser doesn’t pay if the user hits “Skip”. Ad-blocking users are far less likely to watch ads to completion, so I can imagine this having almost no impact on conversion.
I believe this change, if it is successful in blocking ad-blockers, will generally be detrimental to advertisers. It means advertisements shorter than 30 seconds (so, unskippable ads) are now shown to a larger proportion of people unlikely to be interested or paying attention to the advertisement. It’s beneficial to YouTube because they can claw back some of the money they spend serving ad-blocking users videos—that ain’t free. That being said, YouTube is still probably one of the most friendly big platforms to advertisers because of how flexible they are. While it uses the Google Ads system, it’s more friendly than Google search ads…
I missed an opportunity to ask someone who did a lot of YouTube advertising whether they noticed any impact at all from the recent ad-blocker blocking change recently, so this is all speculation.