It's strange when I was a kid I was perfectly willing to watch a barbie movie, I think it was one set on an island kingdom. In fact I thought it had a cool aesthetic.
But at the same time I thought Mlp which was probably still g3 was still girly.
Maybe I percieved Barbie as like Disney while with ponies it was not just feminine but childish. Maybe since it was about semi realistic humans with kingdoms, some politics and some tension, I felt it was more "serious" and "mature" .
I didn't hate feminine stuff as long as it wasn't little girlish.
Maybe G4 was able to give a more mature feel since they the Mane Six were not just little fillies but ponies with jobs