I don't disagree, per se. But the function of the shutdown line is to make nothing happen at our net, so while it's hard thankless work, I can't say that it takes a talent our roster does not have. Getting a top-line capable complementary winger is harder and Hyman is the only one left who fits the bill.
Keefe will have lots of options. If he thinks Hyman is the only guy who could/should replace Thornton then that's fine, but the Tavares line will need to take on more match-ups. Maybe that requires Mikheyev replacing Vesey on it, and that's fine too. This option stacks our top-6 but leaves our bottom-6 looking a little weak.
He could also keep the checking line in tact and throw in a guy like Barabanov or Simmonds on the top line just to see if they could fill that role temporarily.
Or maybe the middle ground option is to take Mikheyev off the checking line to replace Thornton and have Barabanov or Engvall take the spot on the 3rd line. While I like Mikheyev I don't think his presence is as essential to the line's success as Hyman's so that might work.
There's lot of options that I'd be open to seeing Keefe try... except the Hyman-less checking line one.