The gfx were programmed in a system-legal way, and were not "newb-style" at all. In fact I believe the programmer (John Jones-Steele) had a heck of a job getting it to work given the hardware at the time. It was not a simple job and he's a very experienced (and talented) coder.
Looking at his Amiga bio, he does have quite a bit of Amiga experience. And not all his previous games are "system friendly" so I think he knew the Amiga..
However just because he was a good programmer doesn't mean it was the "hardware at the time" that was the problem.
It could have been the developer/production house. If they didn't give him enough time to do a proper port, his first job is to get it up and running and working. After that, you work on optimizing it, and it's possible (likely) that Maxis didn't feel it was worth the effort (time/money) to do that. They probably felt it was "good enough." It might have even been the right call at the time..
I think SimCity 2000 was released about the same time Commodore was going bankrupt.
desiv
