Ok.
So let’s define that you might be asking any of three questions:
1. How can you recognize someone who is yeshivish? This spawned answers such as white shirts.
2. What ideas must you believe in to be considered yeshivish? This spawned answers such as “no college.”
3. What are the central tenets of yeshivishism? This didn’t spawn any answers, although it is probably the one you were asking.
But you see, the question makes no sense because there is no such thing as yeshivishism. The term was invented to describe a communal group–namely the right wing of litvish, and associated with the leadership of the large litvish yeshivos other than YU. But it doesn’t have rules, and it doesn’t have rites of entry. It isn’t a movement, it is (or at least purports to be) the establishment.
While you might have articles and books defining “Modern Orthodoxy” (See. e.g. Rabbis Lichtenstein and Lamm) you will never find a book or article defining yeshivishism.