Correct, but if you’re trying to capture today, these are the lion’s share of what you want to capture.

Indeed, a lot of potentially interesting physical media has no doubt been destroyed, and more still is surely sitting somewhere inaccessible to those who would like to access it. But there is arguably a higher risk in a world where everything sits on servers controlled by for-profit corporations. Which is why organisations like the Internet Archive are so important. If you are concerned about this stuff I would suggest donating to IA, or at least making offline backups of the data you consider to be important (both personally and culturally).