While it is true that the basics of computation did exist in the 70's, it's very clear that programmer productivity today far eclipses what we were doing even 20 years ago. I started coding professionally in the 80's. Today much of what I used to do is now handled by users on their own with spreadsheets and query tools. A small team of 1-2 people today can routinely take on a task that would have taken teams literally 10x as much effort back in the day.
For example, anything involving interfacing computer systems together in any way took an order of magnitude more time back in the day. There were no real widely accepted, simple to use methods available. Networking and communications over modems tended to be so unreliable and difficult that systems tended to be made as monolithic things that just did everything for themselves.
It occurs to me that a book could be e written describing why and how programmer productivity is better today than it was a couple decades ago.
It is true that computer technology has been around a long time. And it's also true that a lot of the best stuff such as Lisp has been around for a long time. But there are all kinds of factors that make programmers complete projects in a matter of days today that they wouldn't be able to 10 or 15 years ago.