Still, I agree. The 68K workstation was essentially obsolete by the time NeXT shipped. Sun was shipping early Sparc systems around the same time. The writing was on the wall. No wonder they didn't stick with their own hardware for very long.
Honestly, Motorola is entirely to blame for losing out on the workstation market. They iterated too slowly and never took Intel seriously enough. I say this as I wistfully eyeball the lonely 68060 CPU I have sitting on my desk for a future project...
Yeah, it seems Motorola lost their lead with the 68040. Intel was getting huge clock speed gains with the later 486/DX2, DX4, etc. From what I recall, a similarly clocked 040 was faster than a 486 on most benchmarks, but there was simply no way to compete with Intel's high clocks.
The NeXT hardware was massively under powered for the software it ran. Other major workstation vendors like Sun were already moving to their own RISC hardware.