Actually at lot of the Hobbit retcons were done by Tolkien himself in Lord of the Rings, and the later drafts of the Silmarillion to tie all three works together.

The Hobbit can be read as a standalone or as a prequel to the lord of the rings.

The white council in Lord of the Rings mentioned happens in the hobbit timeline. It is when Sauron spirit came back in Mirkwood, and Saruman was there at the white council being false because he knew the one ring was not destroyed and desired to be its master.

The necromancer was original just put in the story to get Gandalf to leave the company, after Lord of the Rings was published a much more sinister evil lingers in that name because he and Sauron are one and the same.

Also by rewriting riddles in the dark Tolkien made the ring a more sinister device because blibo's original story as published in the first edition of the ring being a present from Gollum for winning the riddle contest a lie. Too similar to Gollums birthday present story.

I thought it was great when Deltoro was going to do it because he was going to limit the use of CGI and stay faithful to the book.