Because you cannot convince someone that the economy is doing well when they think it's not. Inflation was extremely high for too long, and the wage gap may be closing but it's still absurdly high. "There's a tumor in your brain, but we made it smaller by a third." It sounds like objective progress, but when the tumor is in your brain causing psychological and physical disability. Celebrating the progress makes it seem like you don't care about the remaining problems.

Because the WH keeps telling us we are doing great, but we can see that we are not. The wealthy are doing great, but the working class and poor are not

Because the "liberal media" is a myth, they're all owned by oligarchs who only care about their own cost to borrow capital to fund their VC Ponzi schemes so if interest rates are high they'll try to convince everyone that the economy is bad.

yup on inflation. just look at the fed interest rate for the last decade. you will see how it was raising at a nice gradual pace as obama finished up and then trump bully pulpitted it down to nothing before covid even hit. if they had kept the measured pace it would not have had the bad effects of having to pull so hard on the rudder now.

Because Dems are TERRIBLE at messaging when they’re talking about themselves.

They have been. And they've been shouted down more often than not.

Why isn’t anyone in the liberal media saying how good Biden is doing on the economy?

Because he isn't. It's borderline impossible to buy a house, gas prices are still through the roof, and consumer prices have skyrocketed. The article tries to play down the latter two increases by pointing to the average wage. However, studies show that most Americans have received a wage/salary increase in the last three years. This, in turn, suggests that the average wage increase championed by the EPI (which, by the way, is essentially the liberal version of the Heritage Foundation) is more likely related to a significant increase at either the floor or ceiling of wages. With the Fight for 15 movement gaining increasing popularity over the last few years, and a growing number of states increasing their minimum wages, it wouldn't be surprising if its mainly the floor that's increasing. If that's the case, the fact that the average wage is increasing is relatively meaningless for most Americans.