I run a bunch of assorted businesses, from my digital conversions services started in 2005, to my graphic design firm started in 1996. At the time, I bought top of the line computers (OK, maybe second-hand) and software to run those businesses. Coming on decades later, I'm still running those same computers, and that same software, on those same operating systems. There is a name for these types of computers: Legacy systems (a.k.a. Technical Debt / a huge corporate liability). It's a thorny caveat: on one hand, I've gotten my value out of the hardware & software. On the other, all the bugs and security holes have been discovered for this older stuff, and running it is basically installing a screen door on a submarine. One can only hope that no one is still looking for machines this insecure, knowing there wouldn't be anything valuable on them to begin with?
Why Not Upgrade?
Most of the software is locked to the Operating System and/or Processor, and might have been retired/mothballed with future OS's. Not only had the entire operating system been rewritten from Mac OS 9 to the Unix-light Mac OS X, but the system architecture switched from Motorola to Intel processors - imagine trying to develop desktop software when everything changes drastically every year. Some of that software is locked to the serial number of the machine it's running on (damn you copy protection!). Some of the software was bought before they switched to a subscription model, so it actually just still works without requiring authentication. Considering the raw file formats these files save, there's no vendor lock in!
My legacy machines all have physical backups - computers of the same make/specs/etc., plus data backups of the OS and apps that make them useful. In case a computer finally explodes (or more likely gets stolen), a backup could be setup within hours. Although, there are required OS updates that happen on the network, and there's no saying how long those servers will be maintained (I'm looking at you, Apple - known for ending support for hardware after a mere 7 years).
The Main Gripe: Web Browsers
The point of this missive is that these legacy machines are all stuck with a (very) outdated web browser. They fail at even very basic secure web connections (with many sites automatically sending you to the secure version), barf at jQuery or any modern HTML layouts, and act as stubborn children who refuse to enjoy the ride. Web servers recognize the browser fingerprints, but often simply don't have a low-bandwidth version of the website to serve. One sideline benefit is that you can no longer be distracted by the web browser and the siren call of endless scroll, as javascript fails with complex page handling.
The Need to Stay Current:
I can't live in the past, and I can't run my businesses without access to modern software, so I write this missive on my 'day to day' laptop that tries to stay as updated as possible, and runs modern web browsers like Brave. This machine is lovely, tiny, and powerful, but I feel ultimately underused as a basic web browser and cloud drive point. I can run new software (downloaded from anywhere, but more often from the App Store), and explore the breadth of web technologies, but I do so knowing full well this user experience of dealing with data and apps will soon go away if the hardware designers at Apple have any say about the eventual mashing of the iPad and the Mac, and finally dispose of the local storage concept. I do not look forward to this future; maybe this laptop too will turn into a legacy computer.
(Update April 29, 2022: Just Found Jonathan Alland's Old OSX Projects, where he offers updated utilities that have been resuscitated with replacement dead data feeds...)