I honestly think this couldn't be further from the truth. I get that it's how a bunch of cynical fans see it, which isn't surprising after all these years, but it isn't how the writers/producers/actors see it. Ellen made $40M between seasons 14 and 15 alone. She didn't need to sign on for two more. Of course money is important - it's a job. And Grey's is a massive money-maker. But they have, by all accounts, a great work environment: there's a reason so few regulars have left of their own will over the last several seasons. Since Sara's departure at the end of season 12, all the regular actors that have left have been creative choices, not the actors wanting to leave (AKA... they were let go). Until Justin. When you listen to Camilla, Caterina, Kelly, Kevin, Kim, Chandra, etc. talk about the show, you can tell they're proud of it. They're telling important stories and they all seem to love working together.
The rape episode last year greatly increased calls to the sexual assault hotline that they promoted at the end. They employ women of colour behind and in front of the camera more than nearly anything else on broadcast TV. They hire tons of female writers and directors. They tell stories about race, sexuality, and illness that reach a MASSIVE audience. They've been inspiriting girls to become surgeons, doctors, and nurses for years. Grey's is basically an actors dream, aside from being, like... Leonardo DiCaprio or Meryl Streep.
They may not always stick the landing, but it's rare to be part of something in Hollywood that even tries as much as Grey's does, much less something with as huge of an audience. I think everyone involved knows how lucky they are to be part of this thing. Most actors go their entire career without a part in a series nearly as significant as Grey's.