For more mainstream, search Google for "Alex Kurtsman hard to work with" There are many accounts. I can't cite industry dirtsheets on the discord server unelss you are a member of that server. It's for industry insiders.
Found more from the google search you recommended:
"I worked with Bob and Alex years ago, before they became, well, Bob and Alex. They were and are two very smart and talented writers who understand the business, know what it takes to write successful film and TV franchises, and have shown time and again that they have the talent and drive to make it happen. They don’t pretend to be Robert Towne, Joe Mankewitz, Garson and Kanin, John Huston, or any of the other legendary screenwriters of the past. They are writers for today’s audience. They know their audience, they know how to deliver stories that appeal to that audience, and rather than tearing them down out of spite or jealousy, other writers would do well to try to understand what it is that Kurtzman and Ortiz get that the rest of you don’t."
"i’ve never worked with them but i’ve met them a few times; they seem to be nice guys."
"From what I understand, these guys are actually very nice guys and they take the poison spit that’s thrown their way in stride. "
"Orci and Kurtzman are class acts all the way. They are accessible, respectful and very hard working. There’s no reason to hate on them except pure jealousy."
"Has anyone on this list of comments actually read a K&O screenplay? Not seen a movie and judged it from afar, but read the text? Because I have. Multiple. They have a unique skill set that is nearly impossible to find. They can take extremely technical, colorful action and distill it into clean, concise, efficient writing."
"I’m not a fan of their work but the bottom line is that they deliver what the producers/directors ask for and are reportedly very easy to work with."
"Agree with RB. Met the guys only once but they were very nice. Hollywood wants popcorn fluff and they write it well. They are smart, business-minded screenwriters with good agents."
"Whoever naysays against these two is simply put — a jealous hack. I challenge anyone to find two more generous, hardworking, and classy people in this town. They deserve all the success they get."