A bad recommendation sounds like this:

"I am pleased to recommend [Name] for admission to [School]. [Name] is a hardworking, dedicated individual who consistently demonstrated strong analytical skills and a positive attitude. They were a pleasure to work with and I believe they would be a great addition to your program."

That could be about literally anyone. It says nothing. It tells no story. It gives the admissions committee zero reason to care.

And yet, that's what 80% of rec letters sound like. Not because the recommender doesn't care about you, but because nobody told them what a good rec looks like for business school. They default to what they know, which is usually some version of a LinkedIn endorsement in paragraph form.