I don't think there's any reason to gatekeep this so strongly. The original anime and it's sequel, maybe, but both Tove and Lars Jansson were heavily involved with other series.
https://en.wikipedia.org/wiki/The_Moomins_(TV_series) :
> It is, in contrast to the 1990s series, widely believed to be the most faithful TV adaptation of Tove Jansson's stories, and much closer to her vision. Tove herself had a great deal of involvement during the series' production and was very happy with it (as revealed in an interview with Anne Wood in Simon Sheridan's 2007 book The A to Z of Classic Children's Television). The scripts for each episode were translated from Polish into Swedish and sent to Tove and Lars Jansson, who, if they felt that anything needed to be changed, corrected the script, expanding or rewriting it; afterwards, the scripts were sent back and only then did production of the particular episode begin.
https://en.wikipedia.org/wiki/Moomin_(1990_TV_series) :
> Tove and Lars Jansson were also involved with the screenplay by doing certain changes in scripts.
OK but the article in question describes and reviews the books and illustrations by the Finnish artist Tove Jansson. It is not about a tv-show.
People like the animation too, there's no reason to gatekeep Moomin of all things.
I’m not making a value judgement. In particular the Polish animations are very beautiful.
But the article describes some specific themes in Tove Janssons books which are just not present in the animations.