I wish that were the case but it's just not. Let's take the Index series, it's not good writing but it's entertaining, it has lots of girls in skimpy clothing and a guy travelling the world punching people in the face. Anime studios want to make money. Could they pick up genuinely well written books and adapt them? yes but that doesn't even break even for them.
As for your point about rankings, well they're almost redundant. I'm pretty sure the MAL community rate Steins;Gate as the 3rd best anime of all time or something silly like that. lol. Same goes for your wiki LN list, like anime most people buy because of the pretty characters and not the actual quality of the writing.
*looks a bit further into the novel rankings link*
Mikoto Misaka best ranked female character 3 years running. Splendid.