I'm gonna google "How to bomb Telus Headquarters and assassinate their board of directors" and see how fast they respond

Generally CnD letters are not generated by the ISPs themselves. ISPs don't care what you do unless legally obligated to. When you get a CnD letter, it's usually because someone working for a copyright holder was on a torrent and snagged your IP, then sent an infringement notice to your ISP, who in turn sends a CnD to the current holder of the IP, i.e. you.

At no point does your ISP have to read your digital communications themselves. Any one of your peers on a torrent can tell what your public IP address is, it's inherent to the BitTorrent protocol. Copyright holders take advantage of this to catch pirates.

and a private telecommunications company can read absolutely all your digital communication

Well maybe. It's one of the reasons e2e encryption is so imperative to online privacy. For instance, turning on https everywhere, then your isp can only see which servers you're connecting to, not what's in your traffic to them.

And to point it out up front, yeah the distant end's servers likely have some for of that traffic captured, but now law enforcement has to dig up every company that they're trying to pull info from. Which is significantly more difficult than just relying on a one stop shop arrangement.

And for the best privacy, like security, a multi-layered approach is better. So throw in a VPN, throw in something like a mullvad browser, throw in pseudonymous accounts, throw in different usernames + passwords across accounts, throw in...

The letters from your ISP have nothing to do with them monitoring your traffic. When you torrent, you're connecting to a public network of seeders and leechers. Copyright holders pay people to monitor that public list of IP addresses, and they record your IP (because you connected publicly, in the open, and uploaded or downloaded). Then, they send your ISP a letter reporting that your did an illegal thing, and asking them to punish you. Finally, your ISP sends you a letter making some vague threats and asking you to stop. They might make you do a training course to educate you on why piracy is bad, and they might cut off your internet until you pass a quiz and promise not to pirate stuff again. They go through this charade not because it actually accomplishes anything, but because they don't give a shit, and they're just doing the bare minimum to keep lawyers off their back.