RTS just fell out of favour and isn't popular as a genre anymore. StarCraft was the only one that endured, and even that was a niche interest. If the genre had any appeal then someone else would have taken up the mantle (as we saw with MobA's).
Subscription gaming was going to happen regardless.
Beyond All Reason is building some pretty good momentum. It's more of a TA/Supreme Commander style RTS, so a bit different compared to Warcraft. But it's a modern RTS in active development and growing userbase, which is pretty rare over the past decade.
I'm reading Jason Scheier's book about Blizzard and it specifically says that subscriptions were already the norm for MMOs. In fact, battle.net was revolutionary at the time because it was free while a lot of contemporary systems charged by the hour