I would agree the door-opening effect is true for many walks of life but it doesn't apply to software engineering and similar disciplines. I'm a drop out; I studied economics and have been doing very technical work (low latency application development) for over 15 years now. Worked for UBS, Goldman Sachs, Morgan Stanley, HSBC, etc. No one ever asked me about my degree. They were all (rightfully) interested in what I can do for them.

True passion for the job will carry you much further than a piece of paper from a uni.

Did you have a hard time getting your foot in the door?

After 15 years, most people do not care anymore about your education; but when getting that first job, unless you have an impressive portfolio (and even then...), that piece of paper is huge.

With a recognised piece of paper, you can get much more easily get into a recognised company, which has a trickle down effect for the rest of your career.

I was looking for my first job during the dotcom crisis and it took me about 18 months. I took a semi-programming job at slavery-level salary just to get my foot in. What really helped was the fact that I had spent 3 months as an unpaid intern at a reputable software house 2 years earlier. I remember my friends mocking me back than for being a looser and an idiot for "working for free". This sentiment (entitlement?) is even stronger among young people today. They refuse to acknowledge that when you come in with zero experience and nothing to offer and get free training - you are the real beneficiary.