I'm barely sure that the long term strategy of YouTube is "more ads".
The premium account won't be always ads free
The type of people who have already indicated that they have disposable income, and are willing to pay for a service, are more attractive to advertisers than people who are known to have opted for a worse experience for free
If the LTV of a "good" user (e.g. user who buys things from ads) is X, you price the non-ad tier at X + Y. Y is the premium you pay for not wanting to see ads.
So you're right, but also wrong, in that you can extract EVEN MORE money from the user you were talking about through a non-ad tier.
Companies (Meta, Google, etc) get better at advertising -> LTV goes up -> non-ad tier goes up