Mobafire to me is a place to join a thriving community and a way to share your way to play a champion. My builds always include situational items, and I either test them a lot in normals, and ranked. Also, I welcome every comment with an open mind.
My elo is 1579. Not amazing, but not terrible. As stated above, the average player is under 1200 correct? Well Mobafire is open to the community, and most of the time, there will be trash builds that show up here and there, but you've got to look past some of the bad and ridiculous ideas to find the truly good guides. I know you can always use Solomid for guides, but those are the guides on high-elo games. Most of them are fantastic on getting to a high-elo, and staying there, but in mid-elo, the style of the players consistently change, unlike the high-elo players. Just being honest, most of the high-elo players I see are the same people over and over again. In mid-elo, you have a different variety of players.
Most of guides on Mobafire are around mid-elo. There are some for high-elo, but generally, mid. Who's guide will you trust more getting past the mid-elo part of ranked at least. A person currently IN the area, or a high-level player that has been at the top for so long, they can't really tell you how most players in mid-elo currently play. I've been in mid-elo for a while. The aggressiveness/passiveness of players consistently change. If you're in high-elo, you shouldnt really need a guide do ya?
. Also, if you think you don't need guides, you could be wrong. Looking at a large amount of guides and seeing people's playstyles can inspire you to try to improve your game. EVERYONE has something to improve on 
TL;DR - You could use a high-elo person's guide, but they've been at the top of the pile for so long, most don't keep up with how mid-elo players are. The mid-elo bracket always get different type of players whether they are very aggressive or very passive/farm-y. Mobafire is great for help in the mid-elo range. Most guides are from players in the mid-elo range, but there are some very bad guides. Just look past the bad ones and take grasp of the great ones.
-Xaioli