Well, most of those fall more under the more general umbrella of "strategy". Stellaris is 4x, Rimworld is a management sim, Banished is a city builder. RTS is

Well, most of those fall more under the more general umbrella of "strategy". Stellaris is 4x, Rimworld is a management sim, Banished is a city builder. RTS is stuff like Starcraft/Warcraft, Age of Empires, C&C, Company of Heroes, Total Annihilation, Supreme Commander. I haven't played They Are Billions yet, but yeah, that looks like an RTS or really close to it. So maybe it's not quite dead, but hanging on by a thread! There's also Offworld Trading Company from a couple years ago which is RTS minus combat.