Gossage threw mid to upper 90's fastballs in a time when that was rare, and few batters could handle them, true. I think he would still be a dominant reliever in today's game because he knew how to pitch. The difference between Blake Cederlind (or Geoff Hartlieb, etc.) and an effective major league pitcher with similar stuff is command and sequencing. Parker Markel that pitched for the Bucs last year had great stuff, but got lit up every time because he had no idea where it was going.
Your response is very well thought-out!