I think Clark moving on is overall a good thing. I actually think he's perfect for the Seattle market. He writes as if his audience knows very little about the team and about hockey in general, so that's perfect for a new hockey market. He's also black and extremely "progressive", which is also perfect for Seattle. It also sounds like he'll continue to be one of the lead national writers for any social justice (comments disabled) topics, which he's also well-suited to.
Meanwhile, we'll be getting someone new, and the odds of that person being as uninformed/ignorant about hockey as Clark are (hopefully) quite low. At the same time, given the quality of most of the writers for The Athletic, the odds of Clark being replaced by someone at least as good if not better than him are quite high.
So basically, Clark gets to write for a market perfect for him and about topics he actually cares about (i.e. not hockey) and we should be getting a writer at least as good as Clark but who most likely actually knows and cares about hockey. This looks to be a huge win-win for everyone involved.