You're not wrong, there is a small possibility that this virus does continuously mutate to keep us from becoming immune, and that we don't find a vaccine or a cure.

If so we're pretty thoroughly fucked. We aren't going to manage to wipe out this virus by shutting down the developed worlds economy's because the rest of the world (especially warzones and the like) isn't capable of doing the same. We can't keep the economy shut down forever to prevent spread in the developed world and not all starve to death.

I'd argue that the best response should that turn out to be true is to pour more resources into medical research until we do find a vaccine... which rather requires having functional stable economies instead of us all going bankrupt because we shut them down.