You should always try to have your personal website, as it's almost the only internet asset that you can actually own.
This isn't just about a personal website though. This is Linus Tech Tips (with a staff of about 20 people) building his own platform for delivering content as the article points out. That's a considerable development effort and probably out of reach for youtube creators who are large enough to make a living and depend on youtube, but not large enough to justify that kind of investment.
YouTube revolves around free content - this places creators on the platform at an immediate and significant disadvantage in terms of monetising their audience. Many YouTubers who are stuck in that rut of being dependent on YouTube, despite having a fairly large audience, would likely make a lot more money if they started producing content on platforms which offer better options for monetisation (ideally, their own).
A great example of this is Twitch. Direct monetisation of the audience is a fundamental part of the culture on Twitch. The site is optimised for it. Even before the Amazon Prime subscriptions, Twitch was FAR more profitable than YouTube for creators with audiences of comparable size.