Yes the flicker fixer was a killer, but the real thing that killed the Amiga towards the end as a games machine was:
Flight simulators were not very good on the Amiga, Secret Weapons of the Luftwaffe and the space game X-Wing, there was no equal on the Amiga!
The Amiga was no good at doing 3D due to the amount of writes it took to update the screen, eg 256 colour took 8 writes to update the display, yet on the PC it only took 1 write! An 8 x difference! Then the processor speeds of the PC's were outstripping the Amigas!