The problem with the RTS genre is that people will associate all the RTS genre with only games like age of empires,Starcraft,Command and Conquer,Warcraft and so on...these games are very similiar because they're are in a sub-genre of RTS that never had a name.Take a look at Wolfenstein 3D/DOOM,they are in a FPS sub-genre that is called old-school fps,now take a look at Arma/Battlefield,they are in the military fps sub-genre,they are very different from old-school fps but they are still called as a FPS.Now take a look at Command and Conquer/Starcraft(C&C and Stacraft are to the RTS's what Wolfenstein 3D and DOOM is to FPS's)they are RTS,they are similiar,but people never gave to these games a specific Sub-genre name so they are called just as a RTS,now...take a look at games like Myth,Commandos,Pharaoh,League of Legends,Cities Skylines,Stronghold,Tropico or Nexus: The Jupiter Incident,would you call these games as RTS's ? because technically they are !! just in a different sub-genre.
So...is not the RTS genre that is dying,is the Dune/C&C/Starcraft clones that are rare nowadays just like the Wolfenstein 3d/DOOM clones are rare nowadays.