So Tolkien is a genius storyteller. That's one of the reasons why these stories have survived for so long. Same with JRR Martin.
If Amazon decides to change canon, they're basically saying they can create a better world and story than Tolkien. This is a guy who created LANGUAGES from scratch. Not just made up words, but words tied to our own language roots.
The Silmarillion is epic. It ties everything in the LotR universe together and gives the complete story of why the world exists in the first place and where Sauron, the elves and the wizards even come from. It's a brilliant masterpiece, tying in music, cities and lore in beautifully.
I haven't seen the new series, but if they decided to write their own stories then I can imagine people being pretty upset with it. What an arrogant thing to do.
Also, where is Melkor? He's the real antagonist in these stories. Sauron is just a follower who lingered a bit too long. If they're going to show Aman or the Undying lands and then act like Melkor never existed, then they've basically completely reimagined the entire world of Tolkien.