ooh that makes a lot of sense why many good manga don't get to be an anime, ok a stupid follow-up question: how can a manga get into those magazines ? do they just add it if they liked it ?
It'll depend on the magazine. Yuri Hime sometimes sees a successful author on pixiv or twitter and officially publish their stories. Most common is the author send their storyboards to the magazine to see if they can be published, kinda like it works with books. Sometimes the magazine will make contests with one-shots and produce one series for the author who was the winner. That happened with YagaKimi and Murcielago (although YagaKimi original story was het). Yuri Hime has a lot of one-shot every edition. Some authors for those one-shots sometimes get to make a series, so I'm sure it's related. Also, some publishers go to comiket and such to find artists with potential.
In the end, again, it's not that different than when book authors are looking for publishers around here. Some publishers even make popular fanfics into books.
and i'm kinda confused, are those people behind the magazine the producers themselves or do they push other anime producers to pick a project from their magazine ?
They're the producers themselves, but not alone. They get the idea and try to make a committee to invest money. The producers in that committee are promised that the series has potential to make money in some way, be it streaming rights, CD sales, toy sales, etc. The story having the potential to sell and the publisher being big enough probably help to add trust in the title's success. Usually, the most interested party and the one giving the idea to animate the title is the publisher itself, but not always. When you see an old finished story getting one anime, more likely it was not the publisher's idea.
Keep in mind that those producers might not even watch anime or read manga, so it could be easy to sell a flop to them and it could be hard to sell a clearly good idea. Also, niche markets are hard to be convincing.
Sometimes the studio itself is part of the committee, though.
By the way, Yuri Hime's publisher, Ichijinsha, was a very small publisher until they were bought in 2016 by Kodansha, a big name in the industry. That's probably why we see more Yuri Hime titles being animated now.