I mean, fair. The two big reasons are that your views are worth much more than normal viewers to creators, so it does mean you're helping support the content you watch. Further, the more people who pay for content the less influence advertisers have. All this said, I would assume that $5 a month to your favorite creators (Patreon, Paypal, Librepay, etc) would be worth more to them than a share of your YouTube Premium subscription fee.