It's fairly accurate to say now that RTS games are not dead. though it's important to recognize that the genre is struggling. Thankfully, the current generation of developers entering the space are breathing new life into it.

Why are there no more RTS games?

The way I see it, AAA stopped doing RTS games because RTS is a core PC gaming genre. PC gaming "crashed" (or should I say, became less popular) around 2008-2010. That, and multiplayer first person shooters and MOBAs became much more popular and profitable.

Are RTS games good for your brain?

The study finds that expert players of real-time strategy games have faster information processing, allocate more cognitive power to individual visual stimuli, and allocate limited cognitive resources between successive stimuli more effectively through time.