As someone who has worked on both sides of the coin in the finance world in consumer credit processing, I think the person you are replying to is more right than wrong, but it's also a matter of how you view the idea of complexity.
I've worked on 30+ year old systems where the code base is absolutely immense, but the <complexity density> of this stuff is very, very low on average compared to the magical bullshit that happens on a simple UI render of some template react app in 2022.
Folks had very little in the way of abstractions at their fingertips, and the languages themselves weren't nearly so helpful in helping you manage complexity, so applications were usually long, shallow, and operating under a litany of fixed boundaries that define and drive a significant amount of behavior for you.
The biggest source of complexity was having to manage your own unique `personal operating system` of bespoke resources at any given time, where each developer was carved into an incomplete walking repository of both business processes and software practices with the passing of each year.
To put it more simply, software can't be more simple in aggregate because we can trivially rely on insanely complex components others have built and made available. Components which were simply not available back then.
Yes, the glue on top might be trivial, but even that frequently isn't.
And if anything breaks down, the humans at the top are normally expected to handle it, no matter where in the stack it is.
I've worked on 30+ year old systems where the code base is absolutely immense, but the <complexity density> of this stuff is very, very low on average compared to the magical bullshit that happens on a simple UI render of some template react app in 2022.
Folks had very little in the way of abstractions at their fingertips, and the languages themselves weren't nearly so helpful in helping you manage complexity, so applications were usually long, shallow, and operating under a litany of fixed boundaries that define and drive a significant amount of behavior for you.
The biggest source of complexity was having to manage your own unique `personal operating system` of bespoke resources at any given time, where each developer was carved into an incomplete walking repository of both business processes and software practices with the passing of each year.