Meta is just there to say what is prefered. Typically if you follow it through with your mentality, you are a huge problem with this game who hates diversity in all forms.
In solo que, anything can work if you know how to use them. Sure tanks are considered slightly better then fighters, But thats not saying fighters are 100% useless. They still do their job.
And you know whats funny. I win a ton more games when jungling
then I do with
. You know why? Because i'm a far better Xin player then I am with Sejuani. For the most part, Solo que comes down to individual skill with a champion, and corordinating with your team. Not picking "Meta champs" and expecting a free win.