However, keep in mind that the five year anniversary bundle is still available for five bucks and bundles quite some DLC together.
Regarding the cathedrals & inns, specifically the big meeple: It completely revamps how the game works competitively. By placing it smartly you may get such an advantage that you easily can snack a high value town off your enemy.
Without them, I feel the game is much more head to head focused. It is really important to keep a steady eye on what your enemy does, try to intervene or get a piece of the cake so you both get the score. In the end it is a fight between whoever can defend most attacks, puts himself into other areas and manages to build something great on his own.