Based on what I said, it's a fair criticism that I don't appreciate how hard MLB pitching is. But in fact I do and have expatiated on the topic in the past. A MLB starter has to have the accuracy of a professional knife thrower--but at four times the distance--and the strength to throw it really hard, the skill to throw different kinds of breaking balls, and the endurance to do it 80-120 times per start.
And you're right: Porcello did all those things. But in my view he never had even one good pitch that was really hard to hit, so he had to rely on mixing his pitches, which kind of worked, but he lacked the kind of command that got guys out. Thus his career OPS Against was .750, and in his five years (2015-2019) with the Sox his OPS's against were .787, .635 (his Cy Young year), .826, .698, and .809.