Some things I find notable about plot and characterization

Has a trans woman, doesn't make a big deal out of it (Ticker). She's your contact for mutual aid with the Solaris, helps you hire crew for your gunship, and sonsors the Valentine's day event.

The current story arc is explicitly about two men who love each other but have a very complicated, fraught, and sometimes abusive relationship. They manage to mix softness and anger, betrayal and understanding and do a pretty good job.

An over-arching theme of the game that's been present the entire time is the horrific consequences of Imperialism. All the major factions are, in some way or another, the abandoned, unwanted children of the Orokin Empire. Created as tools for the selfish whims of the ruling class (who are immortal, blue, and nine feet tall. Not because they're aliens, that's just what they considered aesthetic), then thrown away in disgust when they showed independent will. One of the defining traits of that ancient, long dead upper crust is their overwhelming, monomaniacal need for absolute control over their subjects, and how that burning need for control eventually lead to their downfall and destruction. Thousands of years later the Orokin, their god like technology, and their horrible misdeeds still weigh over the system.

There's an entire story arc about union militancy and how labor struggle and the use of violence and outright terrorism in support of workers rights is cool and good. Also features what I think is one of the best labor songs in the 21st century - We all lift together

There's a story arc about a young autistic man who is cast out because partially because he's autistic, but mostly because he sees and understands a problem no one else can. The player has to investigate his sacrifice and take on the burden, setting the man free and setting up the next chapter of the story.

Self-discovery defines one of the earliest story quests and for warframe fans is generally considered one of the most impactful video game plot arcs. A lot of people cry.

There's an entire arc about a deeply alienated, traumatized family recognizing how they have hurt the people they love and re-building their relationships. It's not sappy; At the end they still have real problems and disagreements, but they've also built understanding and compassion.

There's an entire arc about survivor's guilt and redemption, as people come together to remember both the villainy they participated in, and their attempts to help people, and the disaster that ensued. It ends with a commitment to take a second chance to be better.

Found family is another consistent theme throughout the story. If you wanted to sum up the whole plot you could say that it's about your family being who you choose, and who shows up for you when you're in trouble.

One of the major enemy factions is, explicitly, capitalism. They have a religious devotion to profit (I'm the prophet of profit!) that their foot troops are indoctrinated in to and are consistently depicted as just disgustingly evil. The stock market is re-imagined as a winner-take-all blood sport.

Features a faction based, broadly, on indigenous people resisting imperial occupation and violence. Doesn't go in for noble savages, shows them having their own sophisticated culture, religion, and technology. There's an indigenous tracker and naturalist who avoids the typical "magical Indian" trope by combining a deep knowledge and connect to the land with the language of naturalism and conservation ecology, and being your contact for conservation efforts to protect endangered species from the environmental destruction wrought by the imperial invaders. The indigenous people are shown to be spacefaring traders and travelers instead of some isolated, "primitive" people living far from civilization.

There's an entire mini-game where your ultra-deadly magic space ninja wizard trades in their swords and assault rifles for a animal lures and tracking devices to try to remove endangered species from harms way and get them to conservationists who can help preserve and grow the species.

In a lot of ways the game is a mess of poorly meshed systems, power creep, and grind. But it also has some amazing story beats. If you don't feel l;ike playing it there are plenty of enormous lore vidoes that can walk you through the story.