The Short Answer:
R6 is a first person shooter video game where time constraints are usually too short to build effective characterization(s) you find in movies, novels, TV and other forms of fiction.
The Long Explanation:
What is Effective Character Building?
Effective Character Building (characterization) of central and/or secondary characters consists of both past events (backstory) and on-going character arcs which can be demonstrated through various visual and dialogue cues which should organically come out of the situations the characters are put in as the story progresses.
Example of effective characterization:
A) Character Level:
In "Die Hard" (1988) when officers Al Powell (Reginald Val Johnson) and John McClane (Bruce Willis) have a heart-to-heart over the radio and Al tells him the reason he doesn't carry a gun on patrol anymore is because he shot a kid who pointed a toy gun at him. Al's guilt about the past has influenced and keeps influencing his actions/decisions right up until we and John meet him.
Add the fact Al is thrown into one of the most violent situations a first responder can be put in -- A hostage situation with confirmed casualties -- Is also organic to his struggle (arc) and furthers his apprehension to use a weapon unless absolutely necessary... Which he is finally forced to at the end to save John and Holly's (McClane's wife) lives at the very last moment.
B) Story Level:
In the future, Aeon Flux (Charleze Theron) is hired to kill malevolent ruler Trevor Goodchild (Marton Csokas) and free the people of Bregna... Only to find out she was Goodchild's wife in a former life and that Goodchild isn't the malevolent ruler he is portrayed as.
The effective characterization in this story stems from subtle cues -- Visions and fractured memories Aeon experiences -- Such as flashbacks to the present where it is gradually explained Aeon, Goodchild and the rest of the citizens of Bregna are in fact clones of the last surviving population of Earth, and have now found a way to live "naturally" without the aid of the current government which depends on its citizens not knowing they are clones and discovering they no longer need the goverment's "assistance" anymore.
The characterization at this level is the fact it explains why one of the best assassins the world has ever seen can't seem to kill the most malevolent ruler the world has ever known.
It encompasses both the character and story levels of character building and character arcs at the same time. Like the Die Hard example, everything up until the present has and keeps influencing Aeon's and the rest of the character's decisions up until we meet them and find out this truth along with Aeon and everyone else.
Now, what is the main thing both of these examples have that a video game does not?
The more effective use of time and SUBTLE storytelling and character building techniques which gradually form a complete picture of why the characters do what they do (and why) for the viewer at the end of that period of time.
Contrast this to most video games whose "time" is not set (fixed) since it may vary depending on how the player plays the game and is often not a factor with regard to the MP portion of the game at all.
The reason I felt compelled to even post this was because I have been playing real story-based and character-driven games lately, "Elder Scrolls IV: Oblivion, and "Dreamfall: The Longest Journey II", and these games are the true essence of what effective and real "characterization" is and it just will not fit into a game like R6 in my opinion given the nature of R6 and what it is at its core: A first person shooter.
I say this as an R6 fan, a gamer and a former screenwriter as well because...
The press releases (1UP interview with Kimi; EMG article) surrounding R6:5 state things like the devs are trying to give "characterization" to the AI team mates by having one of them "dart his weapon from side to side when breaching" while another one is more of a "heavy-handed type of stance".
The above is NOT characterization. It is just visual differences between the team mates style and tells us absolutely nothing about WHY their styles are different.
The same kind of logic was applied to Lockdown.
Having Renee Raymond yell, "Chavez! Get your *** over here!" is not characterization just as having Louis Loiselle say, "Oui" before every sentence tells us nothing about who he is other than the very superficial (and obvious) trait that he is French.