thinking about fma, one of the things i love about it is arakawa's very intentional worldbuilding. she never gave the story more than the plot needed. we don't get a bunch of flashbacks detailing the characters' lives, eveything that we know about them is only in service of the plot.
the xingese characters are there because they need the secret to immortality to gain their father's favor. and despite this being so interesting we don't really know anything else about them lol. how well do mei and ling know each other? how do their clans stand with one another? anything at all about their other siblings? they get like two interactions and other than the clans just generally hating each other we've got nothing. we don't even get anything about how lan fan even became ling's bodyguard.
then xerxes, a personal favorite of mine. ed and al are kind of casually confirmed to be descendants of a dead civilization renowned for alchemy. are we going to explore that civilization at all? ofc not. anything about hohenheim's past, other that the things you really need to know? nope. we're just generally gonna mention how he's known as a sage throughout both the east and west.
the fact that grumman is riza's grandfather? left untouched. the fact that roy studied under riza's father? you get one (1) flashback.
My favorite manga panels in FMA is during when Mustang was blind and was looking so little and looking absolutely miserable. He looks so done in some panels and like he is one second away from having a breakdown in other panels.
I love the fact that fma is jam packed with disabled representation. Like the main character is a double amputee, his brother has only like 2 of his senses (don't try and say Al isn't disabled cuz cmon), main character's boss loses his vision, boss' subordinate becomes paralyzed from the waist down, main character's kinda friend ig collapses on occasion due to fatigue from hunger (again dude Ling is disabled you can't tell me otherwise), main character's teacher is (this is the only way I know how to put it) chronically ill, and others that aren't as important to the story. And they're all epic as fuck.