I have a 5,1 which was got second hand only for its dual CPU tray and that's now running as a single CPU X5690 machine with RX6600XT GPU and SSD, it serves in my cycling trainer pain-cave connected permanently to a Kickr Bike and a massive 4K LCD screen. It runs latest Monterey beta version and Zwift. The thing is damn stable too compared to what I hear from others using all manner of other different hardware. Zwift it runs in highest detail without a drama. It could do a lot more than that if I needed it to. It could probably handle my work if it had to, it wouldn't be as fast as my 7,1 but it would do in a pinch (although I have the maximum spec 6,1 as well). My original 5,1 I got new in 2010 got fully upgraded with dual CPUs and maxed out in all respects.
This is a nice testimonial of how Intel Macs benefit from both worlds (PC land and Mac world) in long term, e.g in this case more than a decade and still functional today. And this is not going to repeat for Apple Silicon machines. I guess some ppl will argue you could still expand through Thunderbolt bus, USB bus, and PCIe bus (on 2023 MP). I won't dispute but just to point out it's much less flexible than before and with very limited usages.
The folk who designed that machine got it right.
Just a reminder. The architecture is like any other PC workstation from that era. A PC workstation can last this long as well. Upgrades will be much easier to perform by end users. OS support is plentiful, be it Linux, FreeBSD or Windows.
What Apple towers stand out is close integration of hardware and OS, better pick of quality hw components (that's actually to be expected due to premium price), and cool industrial design (sometimes this is subjective).
PCs caught up a lot on hardware/OS integration in the past twenty years. For carefully picked PCs, it's on par with Mac hardware experience. Same goes to quality parts used in carefully picked PCs.
What keeps Mac still kinda unique is MacOS in my opinion. Personally, that's what keeps me from leaving at the moment. Apple hardware (and other iDevices) is secondary or tertiary consideration. So I really hope MacOS won't go downhill and receive proper care from Apple.