Since when did Amiga get IRQ's? Did we take a step backward?
On the Zorro bus, there where only two IRQ lines. Now we have PCI and this has four IRQ lines. In how far this would be a step backwards is strictly beyond me - all those horror stories you might have heard about IRQ conflicts are based on bad drivers that do not check correctly if the interrupt they got is really their own or someone else on their IRQ.
The classic Zorro bus had much more potential for such problems so the drivers are prepared for that.