We like him because we can.
Marco was sweet, he was a team player, he made friends easily and was Jean’s closest friend and confidante, he could identify others’ strengths and could put his faith in his friends’ abilities, and although he could be kind of a pushover since he was generally a softie (honestly you kind of have to be a little bit of a pushover to be such close friends with jean in his trainee years), he was able to identify when something needed to be done and push himself to complete the task (see: him leading the trainees and shooting the Titans at HQ and fainting right afterwards— he was scared shitless, but brave enough to get shit done)
Also, right after we start seeing more of Marco and his interactions with Jean, he’s killed almost immediately, which was kind of a punch to the gut for those of us that were like “oh wow this guy is cute and sweet i think i like him”
some of it also has to do with fanon content. fans have taken what little characterization marco was given and have expanded upon it to flesh him out a little more.
also if you don’t find Marco’s duality symbolism (bit [kind of] in half, a gemini, dark!marco theories which are completely flipside and opposite to his canon characterization) interesting from literary standpoint, i have nothing to say to you
Marco was also an example of how even the best and most promising soldiers can meet a terrible end, all alone, no acts of heroism whatsoever. He was integral to Jean’s character development.
It’s also a little disturbing how he’s the only member of the 104th top ten graduating trainees that had absolutely no backstory.
"he’s boring" is a baseless opinion, and honestly, you coming into my inbox when it’s very much obvious that i ship jeanmarco and adore marco and saying that, comes off as you being an irritating asshole. you dont have to like marco, but you also dont have to try and bother people who do. so next time you send one of these annoying messages to someone, consider the following:
my foot up your ass