TGIF!
We hope everyone is doing well.
Our idiom today is, an armchair critic.
This is when someone speaks negatively or critically on topics they know little or nothing about.
Example 1
My friend is such an armchair critic. Every time he watches football on TV, he yells at the players and refs. And the funny thing is, he's never played or reffed a game in his life!
Example 2
Don't be such an armchair critic. If you think you can fix my car, then do it.