You are right. Times change. Prices drop on SSDs, ram, and graphics cards improve.
So having SODIMM slots and M2 slots for memory is a great idea. Making it easy to add memory or storage is also great.
My Macbook Pro has 16 GB of ram and an SSD.
I have yet to see any good argument as to why iMacs should not have an easy way to upgrade ram and mass storage. And just to get it out of the way making a desktop thinner is not a good reason. Would a few mm make any difference? Not to me.
The Mac Pro was the disaster I thought it would be. It is now dated and you can not update it. The screams of Thunderbolt as the upgrade path did not work out and are dumb.
A real high-end workstation needs slots and mass storage as well as DIMM slots. The Pro is an example of what happens when you let a designer set the specs and not an engineer.
I have no problem with the Macbook Air being thin at any cost. There is a market for that. There is also a market for an laptop with M2 slots and SO-DIMM slots that the user can upgrade. As a MacBook owner, I want a new MacBook but I want one with M2 and SO-DIMM so I can use it for a long time.