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.
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!
Don't be such an armchair critic. If you think you can fix my car, then do it.