Yes, both Lena and Ian are established characters, just like everyone else in the cast. They're 22 and 26 respectively, it's normal for them to have defined backstory and experiences that go beyond "fresh out of high school know-nothing" blank slate from games which are all about corruption. (because, let's be honest, this is really what people who say they want to "mold character from nothing" actually seek)It feels like playing with a premade character in an RPG. I think these types of games work better when we can mold them from nothing rather than getting someone who already has experience in a variety of things.
It's okay if that isn't your thing, but it doesn't by any metric make Lena poorly designed. Her design simply doesn't align well with your goals/interests -- her potential story arcs don't really include "corruption", that's more of a thing for Holly, which you mention. Also, ironically, perhaps for Cindy who has never cheated on her partner before and can be led down this path by Ian (who can also make her enjoy some things she wouldn't before)