I infer from your tldr that your opinion is that this long blog post can be condensed down to a single line conclusion, and that this is a commentary on its (lack of) usefulness and depth.
However, we wouldn't have been know the conclusion without the analysis that went into the blog post. It's interesting stuff for web designers, and to get a general overview of the colour of the web.
If OTOH your tldr was not intended to imply that the blog post was superficial or uninteresting then my rebuttal is unnecessary.
Either way, I find tldr's useful when made in earnest, and about complex subject matter, but too often they are applied in a snarky way which adds nothing. Also, HN should be the sort of place where nothing is too long to read. If you can't be bothered to read it, go somewhere else.