If you're going to provide a TL;DR for others, it's best to read to the end first... telnet was used as an early example, but the writer went on to explain how to target ssh too.

TL;DR Never use anything for anything.

These guys make the "professional" hacker gangs look like a bunch of clueless amateurs.

They have resources, though every technique in this paper is very simple. There are some incredibly talented people out there, and not all of them work for the NSA.

I quite agree. Ultimately, it's all about the resources. Their budget is more than half that of NASA.

The "simple" techniques are enabled by some very sophisticated backend stuff that is just taken for granted in these slides.