why do people say moba fire is a bad place to learn about a champion

The thing people make fun of mobafire users for is sticking to a direct build path laid out on a mobafire guide for them. The thing is each game is different and you should really never be building a specific set of items, so those builds that lay out itemizations are essentially useless if not straight up misleading.

There are plenty of times where say you have a jungle Yi who's feeding but he won't stop building specific full glass canon items laid out for him in a mobafire guide and if you ask him why the fuck he doesn't change up his build to better suit his situation he responds with "these are the items the mobafire guide said to get!" That happens more often then I'd like to admit, and its the exact reason why people make fun of it.

I still go there to see champion scalings and other players takes on item choices, ability upgrade orders, mastery choices, and so on, if I ever feel like learning about a champ just before I test them out in a normals match. But I would never go straight into a ranked game after only reading a guide on fucking mobafire and I would never just stick to a certain build of recommended core items from that site either. So you can still use it effectively, but don't rely on it, or else you'll only add to why people make fun of it's use.

Generally speaking, one gets better at the game of League of Legends by playing the game. Granted, guides are a great place to start for learning specific champions, but ultimately the player only improves by playing the game and practicing.

If anything, go to an op.gg or champion.gg site just to see item builds and maybe averages. Won't tell you how to play, but it'll tell you good items to build (still requires experimenting with your playstyle)/what to expect in terms of scores.