I believe that radio ads can still be effective, but their impact depends a lot on the context and the type of audience to which you want to reach. The radio continues to have a faithful audience, especially in daily journeys to work or in people who use it as a company while doing other tasks. In that sense, a good ad, with a clear and creative message, can capture the attention of listeners that perhaps are not so exposed to digital advertising.
What has changed is the scope. Before the radio was almost the main medium, today competes with podcasts, streaming and social networks. However, that does not mean that it is dead. For local businesses, radio can be even more relevant than digital campaigns, because it connects directly to a specific community. For example, a cafeteria or a mechanical workshop that is announced in the station of the area probably manages to reach close clients in a more direct way