In fact on a grading scale you can see how important the list is to the player. At beginning and poor levels of play (I'm not insinuating anything) the list is vital, and more important than tabletop play. As a player gets better, and more experienced, the list while still important, loses some of its value to the player.
I am not saying that I or anyone else has mastered 40k, or that some of us have "a gift on loan from God". (there are other sites that promote this way of thinking... and yes you know who they are). There is a certain point in the level of play, that the list becomes less and less important. When skill outweighs what they take on the field.
This skill level reaches a point where a player knows how to use his units, and use them to a certain level of efficiency and effectiveness, that makes other people see the light on how these units are supposed to be or can be used on the tabletop.
Do these players play with sub par lists? Not really. By this time, a highly skilled player has refined his or her list making skills as well. While their lists are excellent, they do not always have to be the perfect list.
This I think brings about people playing lists that are not at maximum efficiency and still winning strong. This also brings about some of the contempt we see amongst the Internet stars, saying this guy over there must suck or that list is terrible, or even "there must not be any good players in that tournament or area for him to win with that list." I am saying this is way too much drama. I wish we could move past that as a community, and analyze lists and tactics without the banter.
List building is a skill, playing the game is a skill. However, the list itself is not what it takes to become a top player. The player comes first, as it takes skill to envision how the game will go under a many different circumstances, and to execute the plans on the tabletop to the fullest extent of the army.
I have seen far too many web lists, no matter who they come from, fail. This is because the person that made the list is the best person to play the list. I am not saying that you should not use lists from people online, I am saying take a list and get a game or two in, but ultimately, alter such lists or change them, to suit how you will be playing on the tabletop. Move beyond the list, and become the player.
and of course with less drama..... ( I think I've reached a Zen moment... lol)