That line about "only 20% stick around for the multiplayer" isn't exclusive to RTS. Usually I hear a number like 30%, even for other RTS games, but that's the case across every genre, even for games like fighting games that you think are only there for multiplayer. Only about 30% of people of any game's player base will stick around to play online matches against other people.
StarCraft II is one of my favorite games, but to get back into RTSes, for me personally, I'm looking for two solutions: I want it to work well with a controller, and I think I want to get rid of the fog of war. The controller thing, done well, solves the APM complaint already, since there's usually a speed limit on it. Tooth & Tail, Cannon Brawl, Brutal Legend, etc. give you a "cursor" character such that it doesn't matter what input device you're on, since that character can only move at a set speed. This isn't the only way to do it though; it isn't coded to use controllers, but Northgard operates on distinct tiles and things move at a slower pace such that a game like it could work on a controller without compromise. One of those compromises that games like Halo Wars or Battle Aces have made is that you can't really place buildings strategically, and that feels like they've gone too far. As for the fog of war, I recognize its strategic value, but it wrecks me mentally and emotionally. It's just so stress-inducing, even when I understand how to thoroughly scout. Cannon Brawl does without it entirely, and I can enjoy that game in a way that I can't other RTSes. You still have to split your attention paying attention to all of the different attacks in motion that your opponent has thrown at you, and so it doesn't feel like it's missing something. I'm the star of my own story, so these things definitely feel important to me, but I do feel like both of these things would do wonders for making the genre feel more approachable.
And of course, for me, it's a non-starter if the game is online-only. The two big RTS revivals with the most marketing right now are Stormforge and Battle Aces, and both are online-only, as is that Beyond All Reason game right now. These games have been cooking for a long time, and they're going to be launching into a live service game crash. Their lead developers may take away the lesson that the genre can't be saved when I hope that the actual reason is that customers hate putting time and money into a game that will likely be deleted off the face of the earth in a matter of months, not even years.