There is one camp that says that if it ain't broke, don't fix it. Another camp says, upgrade every time, or else be left in the dust.
In 25 years of IT work, the truth is between the two extremes. Other than Internet capabilities, a Mac Plus from 1986 running Word 4.0 would work just fine for 95% of the users out there. However, what happens on the Internet can fundamentally change things quickly, so one has to keep abreast of changes somewhat, so as not to get stung by ransomware or other threats.
For example, my old, custom desktop from 2002 which sits on a shelf. It isn't even worth powering up because everything it can do, can be done in a virtual machine on my MacBook Pro, for a fraction of the power/cooling needed. Well, not everything... should I have a need to use a 5.25" floppy, I might fire it up. However, I have not come across a 3.5" floppy, much less its bigger cousin at my place in decades. On the other hand, my MacBook from 2008 is still useful, even though it is considered a "vintage Mac" by Apple. It runs the latest OS, browse the web, and do the basics, and has 8 GB of RAM, and a decent SSD.
It really depends on the person. A machine that is usable for me may be just endless frustration for someone else.