Engineers of today aren't better than engineers of yesterday, they just have access to new technology (and new footguns).
I'd rather have a well-designed legacy system that does the job well, than an incompetently designed "modernized" system that doesn't.
Our ability to wield technology has gone up, while our ability to engineer and understand that technology (as a whole) has gone down.
Age should be the most suspect of arguments against the design of a system. Enumerate specifically its flaws and not just that it is old. System design doesn't wear out, it is abstract, like mathematics.
Most of those were extremely optimized for their specific purposes - for instance, screens were carefully designed to fit all the necessary information to complete a task without any scrolling. They had extremely low latency despite all the hardware being potato-grade compared to what we have today.
When latency existed, simple things like the keyboard buffer allowed the skilled user to get ahead of the machine and move onto another task, while the processing caught up.
Today, it's all a webapp with a ton of React, probably 5,000 npm modules, and you get to watch skeletal loading rectangles pulsating after every click (or branded animations on the "customer-facing" flavor). Instead of having muscle memory of hands on a keyboard (usually a specialized one which gave a dedicated key to every important function), the user must move their arm to find touch targets placed at arbitrary places across a 24" touchscreen, and often hunting for functions inside ••• menus.
Obviously, no usability testing has been done on any of these. Or if it has, the only thing tested was "Can a 17-year-old with zero skills ploddingly complete a transaction (the happy path only!), after only 15 minutes of training?"
So yeah, I never listen to any "newer = better" takes.