Porcello compared with very good starting pitchers is not very good even if you evaluate them with fWAR.
His best fWAR year was a 5.1 figure. His other years were below 3 most of them which is not very good.
David Price had a 6.7 fWAR in a single year. Scherzer, Verlander, Felix, etc were/are very good pitchers. Porcello is/was not.