The only longevity issue is the battery, which is a limited lifetime part no matter what, and no support for the newest Xcode, which is unfortunate, but not a real limitation on what I use it for. It's something that I could probably work around by using opencore.
Its kind of crazy TBH. A 2004 macbook (powerbook?) would have been genuinely outdated in 2014, but in 2024, my 10 year old laptop is... fine?
Same thing with my phones. I went from an iphone 4, to a 5, to a 6 to an 11. And there I have stayed. There are a few features that would be nice to have, but not enough for me to fork over the cash. And my old one still does everything fine.
The real limitations are the incompatibilities with new APIs. I fixed up an old macbook air I found at a recycling center for a friend's kid (2011?) and getting it setup took some time since the imaged version of Safari incompatible with modern HTTPS. Once I cleared that hump, though, it was a great machine for youtube, browsing, etc...
Except for the lack of security updates and it chokes when playing 1080p youtube videos and such.
Also, I doubt you've used any Apple Silicon systems. I had a MBP of similar vintage with a discreet GPU, with an upgraded SSD much faster than stock, and the M1 that replaced it was "holy shit" levels faster; now they're on the third gen with the fourth about to make it into portables and workstations.
The new apple silicon is undeniably faster and more efficient, but the point is that there is, for most intents and purposes, nothing that the old machine can't run that a new one can (unpatched MacOS excepted, but OpenCore or Linux solves for that).
Again, I'm not saying that things haven't improved, just saying that a 10 year old computer is still a good machine, in a way that has never been true in the past of personal computing.
Compare a consumer computer from 1984, 1994, 2004, 2014 and 2024. The delta between each step is pretty massive up until the last 10 years.
In theory any computer with a PCI slot can play 1080p with no frame drops.
Devices compatible with Monterey (mostly 2015 models, oldest is 2013 mac pro trashcan) https://support.apple.com/en-us/103260
My iPhone 7 (Plus? whatever the called the big one) still seems a totally serviceable phone from my limited use, although substantially slower than my 12.
It's not been supported for some years now, but I still boot it occasionally and it's far from useless and probably more performant than a low/mid tier Android phone from 3-4 years ago.