You can't rewrite much without the risk of breaking things, so you need a lot more testing. There's a lot of value in the code, so there's more to leverage to add functionality, but the other side is there's more to learn and analyze to efficiently leverage. And when there's lots more teams working on the code, there's more of it and it changes faster than you can expect to fully comprehend; you're continually analyzing and learning.
When I'm off on my own, spiking a new service or library, I can churn out 10k to 20k lines a month; it's very easy when it's greenfield, when there's no team coordination overhead, when you don't need to refactor other people's stuff when you redesign, you don't need to go through full code review cycle, the whole thing fits inside your skull etc. But that doesn't last forever, and it's not business as usual for feature development.
Fixing a gnarly bug might take several days of investigation and end up with a 1 line fix; and delivering that fix might make the difference in avoiding 6 or 7 figures worth of revenue churn. Does that mean it's 10000x less productive?
It's not that far off. I'm taking your example as rather confirming the point rather than refuting it.
When I worked on a big project (several million lines of code) I routinely would code less than 10 lines per day.
For you. For the average developer, on the large scale, I think it is closer to the truth than you'd think.
(Also, not a fan of back-jumping 'goto's or putting executables in git repos. And s/supressing/suppressing/g)
You seem like a fine programmer, but I don't think this invalidates MMM.
Edit: you made Sumatra?? I’ve been using that for a decade, thank you so much for creating it! I put it on all my family’s machines, it’s the fastest PDF reader I’ve found
Here's an example: https://github.com/sumatrapdfreader/sumatrapdf is code written by 2 people (me and another guy).
It's written, documented, tested and bug fixed.
It's 110k lines of code. And it's tight. Good luck removing 10k lines of code and not loosing any functionality.
Assuming 10 lines per day and round-the-clock 365 days of working, that's 30 man-years of work. 15 years for 2 people.
I didn't spend 15 years writing it. It's a part-time effort over 10 years.
The 10 lines per day is off by at least an order of magnitued.
And I don't claim to be spectacularly productive. Jonathan Blow wrote 90k lines of code for Braid in 1 or 2 years.