It's a problem for the Creators. Their stats are lower than they should be, which could have negative effects on their business, like YouTubes recommendation-system not working as efficient as it should be. Similar, would they have a weaker selling-point for companies advertising on their channel.
It should be noted that YouTube income is unaffected by this, as Ads are still shown and counted to people without AdBlockers. So this is only harmful to the creators, and not YouTube.
It should be noted that YouTube income is unaffected by this, as Ads are still shown and counted to people without AdBlockers. So this is only harmful to the creators, and not YouTube.