I'm so confused how does flex 5v5 match making works? I know riot employee's are bunch of crackheads

Been playing ranked flex this past days and what I'm noticing is everytime I'm against full premade and my team is fulll solo que how dafuk does this Match making work I know riot employee's are bunch lazy crackheads but still how is this balanced why aren't full premade groups getting matched vs full premade groups? I mean yh sure I guese just match them with solo ques as long as we get money from skins who gives a fuk about acual gameplay. I mean you can clearly see that this crackheads at riot games only cares about money and not the acual game experienced is when they keep releasing new champions that are fking broken af that you have no choice but to play them or not play them and shit get by them.