Honestly, I think the RTS genre is too hidebound to the origins of the genre. Too focused on trees of units and factories that existed originally because of singleplayer campaigns and trickling out upgrades.
I mean, the current monster of the genre - SC2 - can trace many of its gameplay mechanics and units back to a game that came out in 1994, which was of course primarily designed for single-player gaming.
An RTS basically expects a player to learn multiple games with completely little intersectionality between them - an early-game, a mid-game, and a late-game, wherein you use completely different units and strategies. Given the fact that the designers have to figure out how to make the "core loop" fun in several completely different gameplay modes, and players have to learn all of them, is it any wonder that RTS isn't more popular?
I love the RTS genre - the combinations of base-building and unit command and creativity and intensity scratches all the right itches for me. But every RTS game I play feels like it's bogged down in far more complexity than the game really needed. For a while I had a lot of fun playing with the Cambrian explosion of simple RTS games on mobile because they don't feel the need to bolt on so many mechanics - they figure out what their core loop is and stick to it... but the mobile gaming world has been ruined by F2P mechanics.
I've been enjoying Zero-K lately, which does reduce some of the RPGishness that I think hurts the genre - no upgrading, no teching, no tech trees... you just plop a factory and you start building units. But its mechanics are still incredibly complicated, grown organically over a decade of experimenting within the genre of Total Annihilation-style RTS play. But even then, it's still very tied to Total Annihilation, another mid-'90s RTS game.
I'd love to see more first-class attention to the "core loop" of RTS games, but I'm worried the only people who are truly experimenting with the genre are the mobile developers, and the economy of mobile gaming is an ugly place.