This is a really bleak way to look at digital devices and their role in the world. Should you only write things you want the world to read on a computer, and for everything else, just use pen and paper?
Hackernews is full of people with the skill and position to actually influence what decisions the tech world makes.
It's much less forgivable for engineers and managers that work at Google, Apple, Facebook, Microsoft, etc to be cynical and say "yeah Tech is evil what can you do" compared to the average person, and this site is full of people who are in those positions.
Yes. Anything you write into your computer has the potential to be shared. The same way anything you write and send in the mail has the potential to be shared.
And yet, if GMail published email exchanges of a protected nature between someone and their lawyer, would you just throw up your hands and say, alas, digital communication is cursed?
Some digital activity should be considered private, and violating that privacy should have legal and social consequences.