The article correctly points out that 68k chips fell behind the x86 series. Yes, chunky pixels are useful, and the display hardware should support them. But if the game requires the CPU to draw each pixel one by one, the hardware has already failed. Instead, there should be some specialized processors that do the work. In fact, that's what happened in PCs. Doing all of the drawing with the CPU lasted only about five to seven years, then everyone had GPUs.
(It’s possible to argue Steve Jobs was right when he dismissed the Amiga because it was too much hardware. He knew it would be difficult to keep evolving such an architecture. It’s also possible he was wrong because he didn’t account for Commodore’s chip design and manufacturing processes.)
In any case, by 1992, there were Macs capable of 24-bit color, and the 68040 was certainly capable of pushing enough pixels quickly to run Doom / Marathon / Duke 3D without hardware acceleration.
When Apple went for the PowerPC instead of continuing on to the 68060, the remaining audiences for high-end 68k were not going to move anywhere the same numbers.
If Commodore and Atari had remained competitive longer, there might have been more demand (and conversely, enough R&D effort to tide 68k over until we got to modern "everything is RISC after the decode stages" design paradigms.
A few years later, Motorola was failing to keep up, which is why Apple switched the Mac to PowerPC.
Reason for picking 68000 was bargaining power you had when owning a chip Fab.
"Live with Dave Haynie - Commodore Business Machines C128, Plus4, Amiga" - BilHerd https://www.youtube.com/watch?v=6ZT209i-3Lo Dave reveals Commodore was paying $2.5 per 68000 Hitachi CPU compared to Apple $8 from Motorola.
_$2.5_ per CPU.
The Amiga's dedicated coprocessors let it do things an IBM AT or Mac 512k couldn't do easily.
But the AT evolved into the 386 and 486, and suddenly you no longer needed coprocessors to do the heavy lifting.
So you end up with two issues:
1. Did the Amiga market keep pace CPU-wise? I can see the 3000 and 4000 shipped with better CPUs, but how much was the software ecosystem defined by the 500/600/1200? I wonder if this created a tarpit for developers: the Amiga might have been able to do the same tricks as a faster PC, but the development effort was much higher than just recompiling brute-force x86 code to 68000.
2. Where were the custom coprocessors going? The original Amiga chipset was good, and I'm sure the ECS/AGA stuff was even better, but it seems like it was close to "at par" to a PC with a SoundBlaster and a basic Super-VGA chipset by the early 1990s. What could they use to create a new defensible territory? I could imagine a 3-D coprocessor, but designing something that both impressed today and didn't immediately obsolesce is hard-- see the corpses of a dozen early accelerator vendors.