Disagree. He is getting more than YouTube would ever pay him.
You cannot lose control of an audience you never had control over (if I had to pick between two snakes in the grass, YouTube or Spotify, I'ld pick Spotify). YouTube cannot be trusted.
The rest of your points are either speculative (he might lose his audience according to you or he might gain in audience - who knows?), or envious (Spotify is going to make more money than Rogan). Contract negotiations on this level are competitive. Spotify and YouTube are competing for content creators. Spotify won.
I plan on signing up for Spotify just to watch Rogan from time to time. Who knows, maybe I will find other content that I find interesting. Competition is good. Maybe YouTube will start treating its content providers better, or lose even more content providers.