Elliot routinely talks
to us, the audience. That's a pretty blatant reminder that we're being narrated to by him! His internal monologues aren't just exposition, they're him talking to us, his "imaginary friend".
When Elliot isn't present, things are certainly more reliable, though we have to remember that our context for this world is through Elliot, which colors how we perceive these non-Elliot scenes, as well. We have to accept that at some artistic level, there have to be scenes without Elliot present, but we know that it's still colored by Elliot's reality through tells established in E1 - ie, characters referencing "Evil Corp" in conversations between themselves when he isn't present (it's not the company's name, it's the name that Elliot tells us he has explicitly replaced the real name with in his mental processes.)
"Evil Corp" is adolescent, but I think that's the point. It's not a lack of intellectual rigor on the part of the writers, but on the part of the characters. If you latch onto it literally as Esmail railing aginst dem eeeeeviiiilllll bigcorps then yeah, it would be tedious and silly, but Elliot goes out of his way in S1 to tell us that he that in regards to Evil Corp, he actively rejects reality and substitutes his own.