Did that only apply to new grads with no experience to judge? Or does degree still trump a successful 5-15 year track record?

Big firms care about what schools an associate went to. For partners (10+ years out), they care more about the book of business you'll bring. But there's definitely elitism that lasts well beyond your first few years.

I recall being asked by a visiting partner who was considering having me work on his case where I went to undergrad. At the time, I was a senior associate, so I had a decade of schooling and experience since undergrad.