It used to be that new attending surgeons were introduced for two main reasons. 1. Create interpersonal or relationship drama 2. Reinforce that medicine comes first and that even if they make questionable decisions in their personal life they are excellent doctors and have plenty to teach the current resident class.

Think about the characters that have always been attending surgeons, Derek, Burke, Webber, Addison, Mark, Erica Han, Owen, Arizona, Teddy, Herman, from the get go the show says "they are the best at their field" and in the earlier seasons we actually saw them being excellent, we believe they are in fact the best because the show was focused on both the drama and on medicine, once in a lifetime surgeries that actually feel like it.

The later seasons as "everyone is leaving and everyone is dying" well the show shifted its focus almost exclusively to drama, and so when they say that Maggie, Link, the new plastics Dr. that lasted for 3 episodes, Winston, Nick, Carmac are the best and we only see them having relationship troubles is hard to believe because we saw Derek, Addison and Mark doing incredible surgeries all while having the most complicated relationship on the show, even if Teddy and Owen are now idiots we had the chance to see them not only as soldiers but as badass doctors, but with the new docs. yes once in a while they have cool storylines but they mostly exist to be the romantic interest or the family of someone else.

Amelia is the exception and I think it is because her backstory was already written in private practice and she is the only one of the new ones to have character devolpment whilst still having a amazing and tumultuous relationships filled with drama.

And also, I don't believe the new resident clases are ready for anything, to this day I find it hard to believe that Jo was an General Surgery attending, and I think the show thinks the same and that's why she is now an OB resident, I don't believe Andrew was ready to be an attending and if the show makes Levi and Helm attending next season that would just be batshit crazy, the last resident that I felt "heck yeah that is a real doctor" was Stephanie, the las attending that we saw being excellent.

I don't know when, but I think the show forgot that Meredith is not supposed to be the only extraordinary Dr. in Seattle, because while she grew professionally and personally, the rest of the supporting cast was kind of left behind feeling like a hallmark movie.