You can actually setup ublock0 to do this for you too. At one point I'd used it to blur distracting sites, but like you, I found fully blocking the content(which the blurring effectively did) led to me disabling the block. I'll try this technique out, it's a good idea.

Here's how you can do it with ublock:

  www.reddit.com##img:style(filter: blur(10px);)
  www.reddit.com##body:style(filter: grayscale(1);)

Nice idea, is it possible to gray out only a specific URL or sub?