The credits on a movie always tell a story. You just need to know what to look for.
Over my career, I've received many dozens of credits on so many different projects. From the way my name is spelled, to the placement and order that it's in, to the position title I receive, I can tell so much from looking at so little. Let me break it down for you.
On blockbuster movies, the credits are usually handled/overseen by the Post Production Supervisor. Sometimes the Producers may jump in, but for Below The Line credits, it's usually not something they deal with. Initially, a crew list from all departments is given to the Post Production Supervisor, which is how the credits process begins. From there, the list is vetted. From spell checking, to confirming every name is accounted for, to verifying everyone's job title, generally the Post Production Supervisor works with their Coordinator (and sometimes even their Post PA) to check this list, and communicate the approved final list to the vendor, who actually builds the crawl.
Sometimes, if someone is considered to have done a good job, and they are loved and respected by their superiors, certain people may receive a "Credit Bump". This essentially means, for the duration of post-production, you may have been the First Assistant Editor (for example), but because your Editor loves you, they may fight to get you an Additional Editor or Associate Editor credit. Does this mean you were an "Additional Editor"? Usually, you may have had the chance to cut a few scenes, but your primary responsibility truly was being the First Assistant Editor. Also, the term "Associate Editor" is total nonsense, it's just a way of giving special thanks to a First Assistant Editor who is loved by their superiors. It's certainly not always fair, but that's how it works.
Another way to tell how loved someone is in their credit is too see the placement of the credit. Are they at the top, or towards to top of a department's block? Is their name first if there were others sharing the credit? Are there empty breaks/spaces (large or small) above and below their name? These are all also signs, if true, that someone is being given special credits treatment.
There is always some gray area, and reasons may vary, sometimes it's just a formatting decision that has nothing to do with anything else, but I would say normally, it's clear how valued and respected someone is based on just looking at their credit for a moment.
What are the red flags? By red flag, I mean a sign that someone either lost their job or was not a well respected/well liked person on their team? The most obvious, and worst case scenario, would be to be Uncredited; which means, not receiving a credit at all. Being Uncredited is actually less common than you think, even if the person didn't do well, in most cases, they'll still receive some kind of a credit (unless they were only on the show for a few weeks or a short amount of time). I've witnessed someone who quit early on a show, who was on the project for over a year, get uncredited simply because the Post Production Coordinator was very unhappy with them for quitting early and on short notice. That's an extreme scenario, but it paints the picture very clearly how much power and control the Post Production Supervisor and Post Production Coordinator have when it comes to the credits on a blockbuster movie. And it's certainly not always fair.
There's never any doubt about it - Every single credits list on a blockbuster film goes through many, many layers of checks and vetting. So by the time you actually see it on the big screen in a theater, you can be sure it's EXACTLY as the powers-that-be (on any given film) intend it to be.
Mistakes or name mispellings can happen, but this is usually not an intentional thing. For example, my full name is Joshua, but everyone just calls me Josh. On crew lists, my name is usually Josh. But on paper, officially, my name is Joshua. I like to be referred to as Joshua in my credits - I view "Joshua" as a formal way of referring to me, and "Josh" as a casual way of referring to me. Credits are formal, so I always push for "Joshua" for every single one of my credits. But when I wrap a show well before the credits are ready, unfortunately, there have been more than a few times the final credits come out reading "Josh" (which really annoys me, but I have to let it go - it's close enough, and not the end of the world). If you ever see one of my many credits spelled "Josh", rest assured, without any doubt, the powers that be on that specific project did not consult me with how I wanted my name spelled. I've gotten better at it as the years go by, but sadly I can't catch it every single time.
Other red flags that someone who received a credit was not a very well regarded person on their team can include being pushed further down, even buried deep into the credits where most people will have a more difficult time being able to find them, demoting their position title, pushing them to the back of a list of people in a given department (for example - if there were 5 Assistant Editors, they would be last on this list). Again, there are also times where this can happen that actually does not reflect at all about how said person is regarded, so take this one with a grain of salt. In this scenario, check to see if the credits of a certain job title are in Alphabetical order, or not. If not, you know there's probably some level of politics at play in the order.
In conclusion, credits are not always fair. But so is life. The process is a lot more informal/casual than you'd think, and it's truly a story of who the powers that be on any given show like/favor. I am proud to say that a solid majority of my many credits came out right and correct. So I am happy with my track record. You can't win every time, but considering how many credits I have, I think the overall story is clear - I've been through a lot, but I never gave up, and continue to find success through perseverance.