There is huge difference between early replicators and later, after beating the Asgard, the replicators have infested an entire Galaxy. So blowing up a single sun is far from enough. And the Asgard could guaranteed also have done that. The replicators were only beaten because of the Ancients gate system spanned multiple galaxies, and could transmit the off code simultaneously to them, so the replicators couldn’t react to it.

So in short, the sun crusher is peanuts. Even Samanthe Carter blew up a sun.