Faker for instance who has amazing mechanics and probably best mechanics in the world is not in challenger. Why? Are other players better than him? No, they're not but a lot of them are slight worse than him or the same skill level as him because it's 2019 and people understand this game now better than before. Faker was just the first one who had godlike mechanics, nowadays every korean challenger player has godlike mechanics.
If your skill level is let's say diamond 4 and you're stuck in plat 3 with MMR of diamond 4/Plat1, well then you're in elo hell.
Same thing is for super low elo. Let's say that your skill level is low silver and ure stuck in bronze, then you're in elo hell.
Of course if your skill level is diamond that you not gonna be stuck in bronze or silver or gold but you can still get stuck in plat.
Why is faker in Grandmaster if elo hell doesn't exist?