(It's fine to assert things, but make sure you're right first. Asserting things you don't know to be true is disingenuous, and a bad habit.)
Look at the speed with which WhatsApp was adopted (talking about before the FB acquisition), and compare to Mastodon or Diaspora - there is no contest.
If it's getting newspaper coverage, it's probably not all that niche.
If you somehow use them only for yourself so they run effectively as "your own" (assuming you can and want to isolate them) you run into the same issues I mentioned above.
Your comment in brackets applies very much now ;).
We'd have doused Zuck's dorm room sever in gasoline if we'd known what was to happen.
Let's go back to distributed. Let content proliferate according to novelty and interest gradients. Don't tax it. Don't rent seek.
There are ways to profit without ruining it for everybody else.
I still don't understand how bittorrent (or any decentralized platform) is "your own platform". Most people will always just be part of someone else's platform. Whether it's YouTube, PeerTube, or friendica, it's never their own and IPv6 won't change that. And they explicitly sell themselves as distributed which by definition makes them shared, everybody's, or nobody's. They can never really be your own and that's exactly what their appeal is.
Most people are unable (due to skill, money, or effort constraints) to manage their own platform. And the ones who can don't need to wait for IPv6.
Having said that, it's still possible to hear about independent websites, nobody can "easily wipe me off the internet," and I'm pretty sure my data is far more likely to leak from actual YouTube/FB/Twitter/someChan/etc. than it is from a non-monetized, advertising-free Mastodon instance, let alone my static website. But it's also absolutely true that the best way for me to drive traffic to my web site is getting linked from Twitter or Reddit; discovery is one of the big problems for federated, decentralized networks.
The public commercial platforms offer far more than just a routable IP. You get reach, reliability, resilience, and security (the kind you don't get to build yourself).
Being your own YouTube/FB/Twitter/someChan/etc. platform means almost nobody will ever hear about you, the ones that do can easily wipe you off the internet, coming back is a real hassle, and that your data will leak is basically a forgone conclusion. Being your own Dropbox/GDrive may not need the reach but still relies the other three to provide value. And the list can go on for almost anything you can think of for "being your own platform".
The overwhelmingly vast majority of people have little to no interest in building and maintaining any such platform. It's why so few people actually do it today even when having a routable address. It's inconvenient even for skilled people, let alone regular ones.
I'll wait for a counterargument.