Have a read of this interesting piece by The Guardian's art critic, Jonathan Jones. Titled 'Art criticism is not a democracy', the piece makes two fascinating points relevant to any field...
ONE. Criticism matters. As Jones argues, "iI nothing is properly criticised, mediocrity triumphs".
TWO. No one is going to declare you a critic (or an expert). Instead, it's an exercise in arrogant self-promotion balanced with honest self-assessment. Here's how Jones puts it, "I don't believe my views on film or TV or music are worth anything special. But I do believe – actually I know – that my instinct for what is valuable in art is unusually sure."
I take a simple lesson from this. Everything is worth challenging and criticising, and no one is going to give you the permission to do it. Your choice is whether you want to be someone whose opinion on something matters and what you're going to do about it.