The only compelling addition to the OS that thrilled me was Stage Manager but I guess I will keep on using Mission Control.
Sure - you don't have to junk your Mac the day it doesn't get the latest OS update - or even when it stops getting patches. Heck, I'm still using Monterey even though my Studio is supported by the latest OS - but there's a slowly growing list of software updates that require a newer vesion, so I will need to upgrade in the next year or so. Anyway, this isn't about how long some people can usefully hang on to a vintage Mac that still does what it did on day 1 - it's about how long people
typically wait between hardware updates, and support for the latest software is definitely a factor in that.
The amazing iMac Pro is no longer of interest to Apple.
It's amazing that they managed to fit a Xeon space heater and workstation-class GPU into the iMac form factor - but just because you
can doesn't mean that you should. It wasn't a system that many people buy for personal productivity or re-touching holiday snaps: it's a system for professional or pro-sumer content creation, scientific computing etc. (and even then it was single processor, single GPU system up against scaleable Xeon systems with 50 cores and multiple GPU boards...) - a lot of the target market will have special requirements for displays, specialist I/O interfaces, large amounts of RAM and storage etc. for which an all-in-one simply isn't a good choice. Moreover, they will also have specialist requirements for
displays - multiple displays, arm-mounted displays, displays meeting certain reference specs for colour (not necessarily the highest resolution)...
The value of the 5k iMac and iMac Pro has
always come down to whether the 5k screen was exactly what you wanted. It
was a lovely display potentially worth ~$1000... unless you wanted/needed a different size/resolution/technology, a pair of matching displays or already had a good display. In that case it
wasn't worth $1000
to you and the main value proposition of the iMac went away.
For one thing, the iMac Pro target market overlaps with the Pro XDR display market - but another part of that market wouldn't pay that much for a screen (and yet
another part actually need that $20k dual layer HDR reference display which the XDR
isn't.) - Apple would need to make a 5k iMac Pro, a 32" 6k iMac Pro
and a headless Studio for the none-of-the-above cases and each would have a different niche market. Or, they could just make the Studio/Mini + Studio Display + Pro XDR Display and let users mix and match, while also being able to sell the displays to the much larger MacBook market.
Couple that with the issue that, post Apple Silicon, until you get to a Mx Ultra, there's no longer any night-and-day performance advantage to having a desktop over a MacBook - they're running the same processors - so many customers who previously had both will now be happy with just a MacBook Pro,potentially taking a huge bite out of the desktop market. The Studio Display is clearly designed as much as a laptop dock as a display for desktop Macs. Among the major reasons for choosing a Mac desktop today are that you want to choose your own peripherals or that you're going to be connecting a lot of cables and want to install it semi permanently.
Also bear in mind that the iMac Pro started at $5000. Today, $4000 gets you a M2 Max Studio, upgraded to 1TB and the better GPU
and a Studio Display that is substantially more powerful (modulo post-ASi GPU pros/cons). The M2 Ultra is more comparable to - and cheaper than - the higher-end iMac Pros that cost $7400+