Mossberg had a long career or tech reviews and CEO friends, but I've personally never thought of him as a "thought leader". Moreover, he's unfamiliar to a lot of people.
IMO statements by Chomsky would be more news-worthy. Or by people who might have bigger stakes in staying in the platform-- say if the NYT themselves announced they were gonna be leaving the platform. Mossberg is retired.
I guess the relevance of this piece depends on each person's admiration for Mossberg.
When influential tech personalities, especially ones who are as corporate and CEO friendly as Mossberg, say the are leaving because of a values mis-match, it might be the tipping point for a broader exodus.
That's why it's news.