Stylosa dislikes Mercy. Saying that she needs anything resembling a buff sounded painful for him.
That being said, I’m not a fan of the video. She doesn’t need a tweak to her ult, or some other milquetoast response. She needs 60 hps back again so she can do her job.
Also, he’s wrong about the support meta (especially in high ranks). It’s not in the best spot it’s ever been and Moira (much less Mercy) is not in the great spot he’s ascribing to her.