Starting off: Reused storylines. We have seen the "oh somewhat normal person switches lives with a princess and learn to be themselves" literally three times now. The Princess and The Pauper was the first one, which was a PHENOMENAL movie. Then we had The Princess and The Popstar, which to be honest was not that bad. Sure it was just a copy of The Princess and The Pauper, but the animation was okay, the characters were likable, and the music was great. And then... you have THIS. Stale characters, all of them nearly identical, with bad characterization. Barbie and Amelia are the exact same character. Bland, boring, rich girls. Mediocre songs, stale animation, and awful writing.
Next up: The character designs and modeling. The costumes for the characters are ATROCIOUS. T-Shirts with a ball gown skirt, with stars all over it? TACKY. The previous barbie movies, she's worn beautiful dresses, with somewhat accurate designs to the time period. In this one, they tried to fuse modern designs with royal designs. And they failed. The models of the props were AWFUL, looking like cheap plastic with rough edges. Honestly, you can tell they went cheap with this. Now, I don't blame the crew for this, I would never. The real problem is clearly the companies running it.
The sets: Now, I get they were trying to be clever and make it all look like a dollhouse, but honestly, they failed. It just looked bad and tacky.
The biggest issue is that they tried to be clever with this. We don't want Barbie to be the main character, she's much better when she's an actress, playing someone else. When they write Barbie as the main character, she just melds into the background with all the other characters, until they're a blob of fart jokes, fAsHiOn, clumsy, and dumb moments. There is nothing memorable about this movie, and I think the companies behind it need to go back to their roots. Because if they continue down this road, they will have no fans left. You want animation to be enjoyable for both kids, parents and adult fans. And honestly? I don't even think KIDS would enjoy this movie. 1/10, I would give 0/10 if I could.