I find the new covers much less childish than the old ones.
The general design seems more clean and elaborated even if a bit "boring" maybe for young kids, the square in the middle giving a strict impression to the cover.
The themes of the background are coherent and even elegant for once (feather for book 3, reptilian skin for book 1, footprint for book 6).
In the old covers, colors for the background seemed to be chosen randomly, sometimes it frankly looked bad and not coherent at all (hint hint book 7: Why a green background when Rachel is already wearing a plain red t-shirt?!! Was the book a Xmas edition or what?!)
I was hesitant about the new covers until I was sure about the definition of "lenticular".
It is important to show the morphose on the cover to lure little kids into reading the books
(like it happened for me when I was 9).
I also hope the lenticular square will be made so that it doesn't "go away" too easily.
As for the models... I too think the model for Rachel is not very pretty (at least on the picture posted here). Besides she looks way too soft and her face is a bit chubby. Not very Rachel like.
Eventually, for the adaptation of the text... I don't think they should change the technology part given that it could have significant impacts on the whole plot
but I am not against some changes when it comes to cultural references specific to the 90's generation since I believe that the main reason why those specific references were made in the first place was to establish some connection/proximity between the animorphs and the reader.
Some changes were made in the French translations too (the mention of "Buffy" in book 20(?) was changed to "Dracula", since the TV show was not out in France at the time). I don't think it's a big deal. It happens all the time in series/movies when they are translated into another language so that the audience can get the jokes.
It's even more important if the audience is 10
.