A lot of salty haters.
You would think most people would be excited that a poster is doing something of note instead of piling on to shit on the guy.
People just want to feel important in whatever minute ways they can. This is a method that doesn't take much effort. Here's a guy whose done something, and there's enough in his history here to take a swing at his kneecaps - so you swing.
There's honest criticism (which has happened) there's even-handed negative opinions of the guy's work (fair amount of that) and then there are people who get a thrill out of knowing someone who knows someone really famous and important is going to see what they say, and it feels empowering (in a sour sort of way) to poke a finger in that guy's eye.
It's not really about their opinion, and it's not really about the conversation. It's why so many of these sorts of posts are exhibiting more than enough evidence that the poster in question hasn't actually read anything - because this is mostly about making sure you heard them being "powerful" with their empty bullshit, and nothing more than that.
It's frustrating, sure.
On the other hand, though - there is some spin going on regarding the man's leaving the project. This sort of thing DOES happen a lot in Hollywood. It doesn't mean the writers it happens to are necessarily happy about it. Writers are traditionally low man on the totem pole. Writers are often thrown at a project like spitballs. But again - this isn't necessarily a situation writers enjoy. And it's definitely not one they sign up for beforehand unless it's script doctoring, in which case they know they're just coming on for a couple weeks, taking their check, and then getting the hell out.
Whitta & Edwards were introduced as a duo, pictures, press releases, the whole nine. They were presented to the public as the creative team behind the first spinoff Star Wars movie. That's not something that's done if you're planning on getting rid of the writer before production starts and hiring a new writer (as the Hollywood Reporter article states) to either redo or refine what was originally written.
I'm sure the split was amicable/amiable, because Gary Whitta would like to work with Lucasfilm again, and it's never a good idea to unnecessarily piss off important people in the industry. Make the right noises so people don't have a reason not to hire you.
But I'm also pretty sure this split was not part of the plan, just like - to use the previously cited examples of Prometheus and The Force Awakens - it wasn't really part of the plan to have Jon Spaihts or Michael Arndt removed from the project before it started shooting.
He'll likely still keep his credit (and if the movie doesn't work well, he'll get all the blame that unfairly or not goes along with that credit) and he'll definitely keep his check, but - and maybe he'll come back here and prove me utterly wrong, which would be more than cool - I don't think this was the outcome he was hoping for, to have to leave the project and have another writer take it over.
To use Arndt as an example again - the same noises were made when Arndt was removed from The Force Awakens. But Arndt definitely did not want to have been taken off the project. And he didn't sign on thinking that was going to be part of the deal, either. It's probable this is the same case with Whitta.