The big thing happened when Disney started not paying the royalties on the property they bought. And they would make you sign a NDA before they would talk to you about the fact that "screw your contract with 20th Century Fox, Lucas Films or what ever, we have no obligation to pay you, we just bought the rights not the responsibilities".
Now of course that is not true but when you were looking at taking on the biggest bully on the block, you could not go to the media (NDA remember) and the reason that you asked about the royalties was you needed the money you were kind of up a creek.
This was whispered about in the writing community, especially SFWA (Science Fiction and Fantasy Writers Association) but nothing that you could really nail down.
And then Alan Dean Foster got sick. And he tried to make sure his estate was in order so his wife would be taken care of. And he discovered what Disney was doing. ADF had written tie-in books for decades and his contracts were written most carefully because he know what kind of snakes ran the studios. So he KNEW that he was in the right and Disney was in the wrong. So he told them what they could do with their NDA and went to war. And won.
But now the whispers were shown to be correct. If you were a writer for Disney you were not going to get paid. So it is not your imagination. The quality of writing has gone down hill because good writers refuse to work for Disney.
They have only themselves to blame.
This goes back decades. When The Jungle Book animated movie was first released, they did so right after the copyright expired, so they wouldn't have to pay royalties, and also so Kipling's estate had no say in what they did with the characters.
Now they act like the own the story. (Much like Pooh). Yes, the company that has lobbied extensively for effectively eternal copyright only respects copyright when it is their interest.