You guys touch on the fact that this mulligan rule helps all decks but helps some others much m ore. I wonder if when you sorta account for "inflation" in this equation if the real value of this change for some of these other decks is not net negative.
I can imagine that some decks on the edges of play actually lose viability because of this. Take Mono Red Blood Moon. The deck was not based off a mulligan strategy and really was about drawing multiple synergistic pieces like Moon, Mox, Ancient tomb or Mountian, SSG, Null rod and it already had a lot of redundancy of lock pieces in Moon, Blood sun, Null rod, alpine moon, Chalice of the void, etc. While the mulligan rule will occasionally let the deck trade in a dead hand for something with more play ability, the value of a good hand in that deck may now not be relevant enough against the value of a keepable hand in other list to the point where the list may be pushed out of viability.
I guess in addition to raising the chances for a keepable hand for most decks, this also raises the bar on the assumed power level of opening hands on average and does not do so with the same scale as the increase in keepers. The threshold may just be much higher if the format stays as is otherwise.