Here's the relevant paragraph from that Ellen Pompeo interview in full
"So, again, if you're 100 percent an artist, this path, my path, is not going to fulfill you. I talk to a lot of girls who are on network shows, and they have the same culture problems that we had. Now, I don’t think it’s a secret that we had a real problem at Grey’s for a long time. On the outside, we were a massive success, but there was all of this tumult on the inside: It was a lot of rivalry, a lot of competition. It starts with actors behaving badly, and then producers enabling them to behave badly. And, by the way, I'm guilty of it, too. I saw squeaky wheels getting all the f******g grease, so I was like, “OK, that's how you do it,” and I behaved badly as well. I mimicked what I saw. I'm not perfect. But now I hear other stories from other shows, maybe not to the same extent, but what happens in network TV is that it's super-mundane and there are super-long hours and it's not necessarily the most creative space, so actors get frustrated and they get angry. And there are behavior problems because actors are miserable that they're not Leonardo DiCaprio or Margot Robbie. That's actors: They want to do whatever they're not doing. You could give them a f******g beautiful chocolate ice cream cone with sprinkles and they're gonna say they want strawberry."
I thought the bit about beiing super mundane and not necessarily the most creative space was a good reminder to us the audience as to why the actors can get twitchy when churning out long running shows despite the remuneration , I seem to remember an interview with Seamus after the S5 finale where he talked about hoping his character would get a little more to do, and who can forget Lividity Lanie, who probably didn't need to look at a script to learn her lines towards the end.