I can easily see both sides on this one.
In one way I have little sympathy. It's the same as parents complaining after they show their child a violent anime, that it was a 'cartoon' and so it must be for children - having made that snap judgement without investigating the contents in the slightest.
On the other hand, as the article rightly suggests, there are established conventions in the publishing industry and this book defied them.
They are conventions I personally kinda hate, because they are the reason every Crime paperback looks the same as each other, and every Sci-Fi book is instantly recognisable as that genre on the shelves. But the conventions do exist.
In mass-market publishing terms, sparkly happy cartoon = children.
The publisher and author totally knew what they were doing here and they did it anyway. It's wilfully misleading.
Whether established standards should be enough to absolve a parent of the responsibility to understand what they are giving to their child, though, you decide.
Of course. The definition of what is ugly and what isn't is subjective and nostalgia obviously plays a part in that.
But I think it's quite fair to say that almost nobody would consider a postbox to be an eyesore. It's a functional design but it also has aesthetic elements to it which exist purely to make it look nice, and it's doing an okay job at that.
Contrast to a telecom utility box which is purely functional, a rectangular box coloured in a drab gray or green in the hopes that our eyes might just wander over without noticing it is even there. Intentionally avoidant because nobody wants to see it.
So I very much stand by my opinion on which "needs" painting and which does not.