I think it is a mistake to say that agency is a property of a system, rather than a lens through which we can analyze a system. It truly is useful to describe a thermostat and heater as trying to keep a room within a certain temperature range, even though there is nothing actually striving there.

Much like anything under evolutionary pressure, the viruses that propagate are the ones that do manage (in their normal environment) to keep entropy across time from exploding. Are they "alive"? Meh. In combination with their environment, they act like it though.