Unless there's an explicit reason not to, you should indeed assume that men in the middle will look at what you pass by them.

Then you have to decide for yourself if you're OK with that or not.

I know Microsoft looks at my files when I put them on my OneDrive. I take that into account when I decide what to put there. I know Google reads my mail when Thunderbird sends it through their SMTP servers. I know it'll be read by some unknown parties along the way to the recipient. I take that into account when I write my mail.

If I pasted a URL into a feed reader, I'd most certainly assume the app, and by extension its creators, would access that URL and read what's there. I'd take that into account when using the app.