Wait a second? Isn't Rhythmic Music nothing more than a huge umbrella term, like Alternative is? Hip-Hop, EDM, Synth-pop, House, Disco and so on could be called Rhythmic. Yes, traditional rock doesn't have as much of a draw as it used to. However, isn't some of this so-called rhythmic music an evolution of what was popular in years past. For instance, hip-hop has taken a lot of influence from 70's and 80's pop music, such as Phil Collins. Heck, the most popular groups on Alternative radio today are not traditional rock groups, but modernized versions of 80's style synth-pop groups. Bleachers, Walk the Moon, Chvrches and Imagine Dragons are the most popular groups on Alt right now, groups that were heavily influenced by the likes Depeche Mode, New Order and the Eurythmics.
Also, the reason why Country music is so popular on the live circuit is the power of live performances, which has been the recurring theme on this thread. Well, if that was the case any band could become really popular if their live performances were engaging. Tool, Cocteau Twins, any band that could engage their audience in an extremely effective way.