You're confident in what you do. Do it, and do it well. Let that speak for you. Let it be your "credential". Those who do it better, well, they have higher credentials than you.
An Ivy League degree may mean a better education. Or, it may not. It may mean that their application looked better than yours. Or it may mean that they got in on a "legacy" application, because five generations of their family went to that school. It may mean a wealthier family background, or a really nice scholarship, or it may just mean a really big student loan.
Don't judge by the degree. If they flaunt the degree, it means that they are hung up on the degree, but it doesn't mean you should be. (And why are they hung up on the degree? Maybe, because of a bit of insecurity. If you have to show off your university credentials at your job, maybe you aren't convinced that your job performance shows you off...)
But "I've always been a slacker when it comes to education"? Well, don't be a slacker when it comes to your job.