Bandit LOAF said:
There's an existential problem with going on about Star Destroyers being able to wipe out entire planets -- if it were true, there'd be absolutely no point to anything that happens in the Star Wars movies.
Oh, no, we need to risk it all to stop their planet destroying Death Star... which is different than the average enemy destroyer... in that... it's slightly faster!
Well there's two problems with the basic approaches.
First is that the SWTC people take what's said about Star Destroyers too literally. (As in when it says "a civilization to slag" they calculated based on the literal interpretation of slag.)
While the second argument of "it makes no sense" is when it ignores the context of what the statements written in universe materials is.
Consistently it's been said that they could essentially bombard a planet's civilization back to the stone age, but always with the caveat that it wouldn't outright destroy the world, just sort of you know, level the buildings. And it seems only if the world's not shielded by one of those planetery defense shields.
So I mean there's nothing inherently wrong with a Star Destroyer being able to burn/scour the surface of a planet, there's enough caveats that something that can outright destroy a planet like the Death Star (and most likely do it through a planetary shield) is useful.
Bear in mind also, Kirk had a few lines about destroying the entire surface of planets in TOS, which given the yield of antimatter explosives and the like is probably possible in theory, just never backed up by the vfx. (Which are in any case always understated.)