Nichjou is a surreal, exaggerated comedy, but I don't think surrealism or exaggeration are what Nichijou is about. Instead I'd say that Nichijou is about giving meaning to the day-to-day. What Nichijou has to say is that, although our small lives might seem meaningless and shallow in comparison to the grand scheme of the world, they still have the same importance as the spectacular, the awesome and the unbelievable. And Nichijou delivers this message in in two main aspects:

First, the obvious. Nichijou is Slice of Life comedy in which every day-to-day scenario gets exaggerated to the absurd, elevating the mundane to a new level. This is made using exaggerations in the animations, which is possible thanks to the general art style of the show, because if it had a more detailed look, like other Kyoto Animations shows, such as Hibike! Euphonium, the exaggerations would look out of place and would be incoherent with the tone evoked by the art style. That is why the simple design of the characters fulfills its purpose greatly.

Secondly, there is something wrong in what I said. Not all characters in Nichijou are what could be called "normal people". Hakase is a mad scientist, Nano is a literal robot and Sakamoto is a talking cat. But, although the apparent unbelievableness of these characters, they are treated in a normal way. The central theme of Nano's character is how she wants to be a normal girl, because at the end of the day, she acts and thinks like one. Behind the apparent strangeness of Nano there is in fact just a normal person. And through the series, all the characters end up treating her as just that, a girl, a normal person; and the only character that doesn't, her teacher, fails every time she tries to uncover any "secrets" about Nano. Nichijou is presenting these incredible, unbelievable situations and taking them down, and making the viewer realize that these characters are still human.

What Nichijou is telling us is that the incredible and amazing people we see are as human as every other mundane citizen, and their lives don't have more meaning that every other person lives, because the meaning of life is not in life itself, but in how you perceive life. What Nichijou is saying is that your life, as meaningless and useless as it may seem, can have the value of the unbelievable.

Lastly, I want to remark one element of the series that is more notable in the rewatch. All the gags in Nichijou seem unconnected, but once you have already watched the series once, and kind of know the characters and some events, you can see how some gags foreshadow others, and expose a development in the characters. This development doesn't happen in the main scene, but in the background, and it holds great importance, as it gives the school on Nichijou a real feeling. Like you are not just watching some random characters, but an actual community of humans that interact with each other, being an element that grounds the elevated style of the series.

As I have explained how Nichijou perfectly achieves its goal, and, personally, I find its message to be very good, I award this series with a 10 out of 10.