Meanwhile, at Riot HQ

While I can't speak on how other teams grab player feedback, I can speak on behalf of skins!

As you've probably seen, we post PBE threads about new content. After a couple days of the content being out on PBE, we collect player feedback from several forums (these boards, S@20, Reddit, Skin Spotlights on YouTube, etc). We compile the feedback in the form of screenshots, quotes, etc, and email them to the team who is working on the skin.

With that being said, there's plenty of feedback that we see and use, but don't comment on. It'd be pretty hard to reply to every comment made about a skin, be it positive or negative feedback.

At the end of the day, we can't make everyone happy when it comes to new content, and from my personal experience, especially with skins. To be honest, it sucks. Making one skin to please everyone is pretty impossible, but we do our best to voice the opinion of players and to try and make as many happy as possible, based on the commentary we see on the boards.