When has Disney ever trashed the prequels? Kind of odd, as prequel characters are quite prevalent in the theme parks. Jar Jar being the exception.
Let’s not pretend there weren’t a number of cast and crew involved in TFA championing it as a “return to form”, Simon Pegg being Simon Pegg, and the huge marketing push endlessly touting all the practical effects in the film. They didn’t come out and say “the prequels were crap and this is better”, but in a lot of instances they may as well have.
Let’s not pretend there wasn’t a section of the fandom that didn’t like the prequels. You can’t blame certain individuals for trying to reassure those fans and get them to come back. I will concede that the practical effects angle was overstated, as the prequels did have some practical FX, but every movie has some spin doctoring going on in the publicity dept. The sequels and the story films still reference the prequels.
I fully expect there will be some subtle and not so subtle return to form shade thrown at TLJ in the coming year as we get closer to Episode IX. I don’t think that’s Disney’s official corporate stance though.