OP is right, it will survive bar some destructive process, and it's in your control. Hosted content is susceptible to destructive processes as well, Data loss? Gone. Org gives up and shuts down? Gone. Deindexed or lost in some future search LLM to rule them all? Gone. it's mostly out of your control.
This all just points out how hard it is to preserve anything over a long period of time. We think of the things in our lives as being permanent because they mostly last for a good portion of our lifetime but once property or information changes hands all of the tacit knowledge about it is lost. The next generation doesn’t see that notebook as important so it is just as likely to end up in the trash as in a box in storage. Even if they do try to preserve it there are many ways it can be destroyed or degrade or simply be lost.
Even the seemingly simple thought experiment of “deliver a one sentence message to a person living at your current address 500 years from now” is nearly impossible using ordinary means available to an individual.
This discussion brings to mind the monastic practice of copying texts for the purpose of preservation [1]. An interesting practice I learned from the sci-fi classic "A Canticle for Leibowitz" [2].
We aren't immortal, so it won't be in your control forever regardless of how you record it. Over long periods of time, the internet is far more accessible for long term storage of someone's writings than physical media. An unsheltered person with a library card could write about themselves and that would be preserved on archive.org, copied by other/future archival websites, copied by individual data hoarding enthusiasts, etc. There is almost zero chance a notebook would survive any significant period of their life, let alone after their death.
Maybe for people with stable families and enough disposable income to easily store boxes of printed material for generations, physical media is a good choice. But not everyone has progeny to pass things on to. Not everyone has the ability to safely and securely store generations of writings. A house fire in your lifetime may be unlikely, but what about in 3 generations worth of houses? And there is zero redundancy. If archive.org shut down tomorrow, there are people on reddit’s r/datahoarder that have copies of various portions of it. Data would be gone, but not all of it. If a tornado hits your house tomorrow, there is no one that has copies of your handwritten notebooks. 100% loss.
