I can sort-of see how that might come about, if the purpose of the philosophy class was to practice making arguments, using philosophy merely as providing something to argue about, but one thing I have learned about it (and most other things, for that matter) is that if you don't find out if your idea has been floated before (spoiler: it has, at least if it has any merit), and, most importantly, what responses have already been made, the class will spend all its time splashing around in the well-stirred shallows.

At first, it seems odd to me that your English professors acted in the manner you describe, but I guess most of them have chosen to ride the criticism wagon, rather than the creative one.