I understand the point you are making and I do agree with it to an extent.
However, I would argue that doing a respectable subject (a traditional one, humanities or science-based) at a decent University is not a waste of time. Like a previous poster said, at the age of 18 you are free of responsibilities and it's certainly more convenient to undertake a degree at this age when you're not trying to hold down a job, bills, kids etc…
Let's face it, if you're academic and you have the ability to go to a good Uni and don't, it's a bit of a waste.
I know that many grads come out of Uni and go into menial jobs, but this is not the end of the line. Many of my teachers had different jobs after graduating before they decided to have a change in career path and take a PGCE, because they already had their undergraduate degree in place they only had to spend a year doing this as opposed to doing three years of undergraduate study plus another year doing a PGCE.
Many kids have the wrong attitude towards Uni, not taking out any real world experience so when they graduate they have nothing. What counts to an employer is a well-rounded person, i.e someone with a degree, work experience (or even better, a dedication to a paid job for a number of years) and enthusiasm.
I have just started my first year at a Russell Group Uni and I am commuting from home, keeping my retail job which I have had since I was 16. As someone my school put forward for Oxbridge entry, I had exactly the same view as you had in year 12 and 13, and I didn't apply for University. I was disillusioned with the whole world of academia and University study, especially with a working-class family who didn't agree with it. I flunked my A Levels, and I was very, very lucky to come out with the grades that I did and absolutely staggered that I got accepted on my first application through clearing.
There are many people that I work with in retail now in their late 20s who regret not working harder at school and going into HE because, yes, they've moved out of home, become financially independent, some have kids, which of course, yes, is good, but now have no parents to support them and too many responsibilites to 'risk' taking time out of work for the chance of doing something better. Because higher education offers you a chance,
if nothing else.
It's great that you're taking a gap year but don't fall into the trap believing that in the end you're going to be better off than your peers that went to Uni. You may be better off for 3-5 years whilst they're slumming it at Uni, but once they've graduated they have the degree behind them, and many do go into better jobs, as like you said, graduating gets you in higher. Even those that go into the same menial job you may be in, they have more ability to progress through the higher positions in that workplace, or that job may just be temporary as they apply for yearly graduate fast streams, or save up to do further study and qualify as something else. Finding jobs is harder today so there is nothing wrong with working somewhere menial for a few years while they look for somewhere else… also, there is nothing wrong with them staying in that job if they like it. But remember, whilst they are now setting up their lives, yours is already established. But if you want to progress, it's going to be very difficult, because how are you going to support yourself through a degree? At least those that went to Uni had a chance, and they still have a chance, because they still have a degree, and will have it for the rest of their life.
Remember that, all you do by going into work instead of University is growing up three years earlier than everyone else.