Why modern escorts perform cruiser missions

If modern frigates are cruisers by role, what does that make a destroyer?

A cruiser focused on air warfare, while a frigate is generally the anti-submarine variant.

Modern escorts can be understood as cruisers by role because their peacetime missions resemble cruiser work. Within that comparison, destroyers are the air-warfare variants. Frigates are the anti-submarine variants. Function can therefore group ships together despite differences in their official classifications.