Dead time was doing something
A long gap between pitches was mostly waste, and it was not only waste. It was when a pitcher reset after a bad sequence, when a hitter refused to be hurried, when a catcher talked someone down. Compress it and you compress a psychological contest that used to be part of the sport's texture.
I still think the trade is worth making. A game with less standing around is easier to love and far easier to introduce to somebody new. But describing it as purely removing waste undersells what changed.
Rhythm is a weapon
Some pitchers thrive on speed, keeping hitters unsettled by never letting them settle. Others need the pause. Any rule that fixes the tempo therefore helps one temperament and hurts another, and that is a real competitive intervention, not a neutral housekeeping measure.
The interesting question over the next few seasons is who adapts. Sport usually answers rule changes within a couple of years, in ways nobody predicted, and the players who benefit will not be the ones anyone nominated in advance.
Keep the goal in view
Shorter is not automatically better. A tight, tense evening that runs long is a wonderful thing; a brisk, empty one is still empty. The goal was to reduce the parts of a game where nothing is happening, and that is worth protecting against the temptation to keep cutting for its own sake.
So my measure is not the clock. It is whether a viewer's attention is asked for continuously rather than intermittently. On that measure the change has clearly worked, and the sport should probably stop there.
What I will be watching for
The most interesting consequence is generational. A player who came up under the old rhythm learned to use it; a player arriving now never had it, and will build a routine around a tempo that is simply the way the game is. Within a few years the debate will sound as dated as arguments about earlier rule changes do today.
Until then I would treat every claim about what the clock has done to results with some caution. Seasons contain a great deal of noise, and the temptation to attribute every shift in scoring or pitching to the most recent rule change is strong and usually premature. The honest position is that the watching experience improved, the strategic effects are still settling, and both things can be true at once.