Yeah. Absolutely unreadable. The site doesn't even override the scrolling in Javascript! Not to mention there's not a single pop-up on that site. Now, how I am supposed to know that my privacy is important to them?
Gosh, you weren't kidding. Even ignoring the painful contrast and small text, the background characters not being regular (lined-up) is setting off my ADHD something awful, I keep getting distracted, couldn't make it through the first paragraph.
To me, I use the reader mode on my browser because it allows me to have a consistent view for every article I put through it. I can have a font size, and background colour that is comfortable for me to read. I do however notice that reader modes seem to be used more so for making horrible looking websites like this readable.
Seems totally fine to me.
It seems browser dependent, I also needed reader mode in desktop Firefox, but intrigued by your comment found it seems fine on FF Android. (In the former the background was way more disruptive, the pattern on it interfering with the text so much as to make it illegible.)