This was only a good solution for Apple. For users, it limits the possibility of expansion and the freedom to use any components.
Please re-phrase that: "The freedom to use any [PC] components." As freely as a PC let you use them.
But how free is that? It's quite a mixed bag.
Mac was never PC and no one with clear thinking is confused about this. It's an obvious a point of history. And it's Apple's main selling point!
The edge of compatibility of Mac SW with PC hardware has always been very limited.
Mostly PC "freedom" means add-on storage and USB.
Consider where the Intel Mac began:
2006 15in Macbook Pro
Technical specifications for the MacBook Pro "Core Duo" 1.67 15". Dates sold, processor type, memory info, hard drive details, price and more.
everymac.com
"1.67 dual core, 512M RAM / 80G HD"
This was in the era of what we think of as modern PCs: DDR, PCIe, SATA, USB.
There are no benchmarks listed because Geekbench had not yet occurred. You had to boot Windows to bench. But if you could Geekbench 6 it, the score would be something like 175 SC / 250 MC, where an M1 is 2500 / 10000. Its USB limits storage to 30 MB/s compared to 1000 MB/s for USB 3 gen 2 common today.
—And the benchmark don't consider the accelerators that add amazing performance to M series.
In time of M-seriees, built-in RAM, storage and graphics are hugely plentiful. And USB is has kept up.
Since Mac was built from Intel, there have been 13 Core series gens, with 4 gens of RAM and 4 gens of PCI.
(Interestingly, two of the PCIe gens occurred in the last 3 years.)
With backwards compatibility there's always a cut-off and where a cutoff hasn't yet occurred there are many tradeoffs. Everyone knows this, but some people hang onto to an idea that PC is infinitely backwards compatible because Windows looks basically the same as it did in 2000.
So an argument about "expansion freedom" pre-M series is not strong.
I'll repeat myself:
//Basically, what M series did was rearrange the edge of modularity to be at the Thunderbolt port//
The module you upgrade is now the integrated unit of a cube. If you want a generational advance, you replace the cube which has a price-point overlapping a high-end mobile phone or GPU.
(Interestingly—part 2: the phone's total system performance is close to the cube, it's optimized to run on a battery and has one simple port. The GPU has become a phat accelerator for 3D and neural nets. Apple is keeping up with these trends.)
The cube's serial IO port lets you expand plenty of stuff, including storage that's connected by inexpensive, fast 1GB/s USB, which because of chip evolution is running at 20x the speed and 20x the capacity that hard drives were when Intel Macs were introduced. Everything in silicon is 20x the OG MBP.
If you have lots of spinners, connect them via USB using cheap outboard case. A 5Gbps USB PORT is fast enough to run 2 of the latest 20T spinners at full speed at the same time, and 1 Thunderbolt port has enough bandwidth to run 8 5Gbps USB ports in tandem.
As cube evolves, if you don't need all the latest hottest chips, choose an older device readily available in the aftermarket. Users of old PCs are happy with massively down-rev kit. Users of Macs can do the same. The Thunderbolt 3 mini has been around for 7 years.
And as to old software. Old Windows is as hamstrung by incompatibility as old macOS.
The more you think about it, the less meaning there is to the idea of "expansion freedom" of Intel. The idea is drained of any substance.
I don't understand how anyone doesn't see the M series as an excellent "solution" for everyone who wants Mac, across the board. And it's the natural evolution of PC, it's just not a PC.
If you want freedom to have some true meaning, the dream of "hackintosh" lives on, in the form of Linux, and there is Linux on everything. Inc ARM.
