Jack Morris is, at best a borderline HOF candidate. You can make some arguments for his membership, but the claim that he was "the best pitcher of his era" is ludicrous on its face. Here is a list of some of some of the pitchers who won the Sporting News Pitcher of the Year or Cy Young awards while Morris was pitching:
Of course all those pitchers also pitched before Morris began his career or after he ended it. But, not only did Morris never once win the Cy Young award, he only got 6 first place votes over his entire career. In short, during his entire career he was never considered the best pitcher even in the American League.
The only way you can claim Morris was the "best of his era" is by making that question the same as asking who was the best pitcher who started his career in 1977 and ended it in 1994. There isn't really much, if any, competition for that title.