No, what I am trying to say is that Sin doesn't go around randomly shooting gravity attacks that destroy half of Spira and attract Moon normally.

As have been said, Sin that is now just summoned without consciousness from the empty shell of what was Yu Yevon is simply programmed to protect Dream Zanarkand (and he attacked it only thanks to Jecht, to what extent it was Sin and Jecht that actually destroyed half of the city, who knows), destroy big dangerous machinas and keep killing big formations of people so DZ cannot ever be threatened.

It's also obvious enough that Sin normally isn't so aggresive, it doesn't even really attack Bevelle and Luca, if crusaders can protect those cities, the Sin isn't really trying. It probably just swims in the endless seas for the most time being relatively harmless.

Since Sin been around for so long and been dead so little yet the Spira is still around, even if there was no way to kill it, it would be as you called it, more like force of a nature, you can't really kill tsunami or hurricane and they kill and destroy cities as well.

So really without Seymours intent to kill all Spira with Sin, it wouldn't really matter that much.