I doubt that code written today is better than 30 years ago. We have much better tools, including source control, and much better hardware, but that's enabled us to write vastly more code than was feasible 30 years ago. I think there's been a choice about whether to use that extra power to write either better code or more code, and we've veered sharply towards writing more code. Some if it is better, but most of it is probably worse.

30 years ago was right at the start of my 'career', learning to program my ZX-81 as a pre-teen. I learned to program it in Z80 machine code, because it only had 1K of RAM and you couldn't fit much BASIC code into that space. (Also, there was no assembler. You had to write the assembly code on paper, manually convert it to machine code, and type in the bytes into a comment line in a BASIC program.) My experience with the ZX-81 isn't that much different from what the grownups had gone through over the previous 10-20 years with teletypes, mainframes, and the other early PCs.

The degree of low-level fiddling and knowledge needed to program computers back then led to much more careful analysis and understanding, I think. No one had to tell us to design first before we sat down and started coding, because there was no other option. And not just design; we had to run the code in our head and debug it before it was ever put into the computer. That's a skill that I've pretty much retained today, 30 years later, and occasionally I still use it. (eg: During code reviews, or thinking about a problem I'm working on while in the shower.)

Younger developers, mostly, haven't gone through that kind of experience. I think it makes a difference. I'm really happy about the existence and popularity of the Arduino and similar open hardware platforms because they bring back that bare-metal level of software development. I'll bet that today and in the future, the best programmers are going to have a shared experience of working on devices like that when they were young.

I am around your age and started then as well, also Z80. In my area it was rather normal to just write and run hex in your head. I still know the whole instructionset in hex as I wrote so much code with it. I totally fail to see the reason why anyone did use an assembler for that; I can just read and write the hex codes and did. Besides the time it took to get back after a crash it did not take much more time to 'get shit done' then as it does now. There were just vastly less programmers and thus less code was written. Unfortunately I don't have my 80s code anymore but my output has not changed much; better code and the code does more because of the libraries we have now, but it's around the same amounts. Running code in my head is great and was easier with something limited as an MSX (or zx for that matter); but it gives me a lot of advantage I believe.