The New York Mets have perhaps the best pitcher in the planet in Jacob deGrom and a solid, mid-rotation arm in Marcus Stroman. After that, they have rookie David Peterson, who had a very good debut year in 2020, and Steven Matz, who didn’t fare so well.
As a result, they need to sign (or trade for) a couple of pitchers, at least, to shore up the depth in the rotation. Nowadays, MLB teams need between eight and ten starters to navigate through a full 162-game season. Between injuries, ineffectiveness, suspensions, and other unexpected scenarios, depth can disappear at any minute.