I will explain this again as simply and slowly as fucking possible.

If every champion does the exact same singular thing, has the exact same singular tactic, builds the exact same items, has more or less the exact same kit, you have overspecialized, and you are going to have a VERY hard game in an atmosphere where you are desperate to surrender the very instant something doesn't go your way, as it is.

A team of five assassins is overspecializing.

A team of four assassins is overspecializing.

If you do nothing but melee as a team, you are overspecializing.

If you are all AD, you are overspecializing.

I have pointed this out endlessly in the past, and because the average player here is less well-read than a prisoner in a North Korean forced labor camp, I might as well be trying to teach quantum mechanics to a gnat. The universe could cycle another four hundred septillion times, and you would STILL never come close to even hoping to begin to grasp the most basic concepts of homogeneity.