I personally disagree with the change, but can only speak from the pov of a ("casual"/MM) player and viewer.
In my view, each half only becomes interesting during the final couple of rounds where each team had the chance to frisk each other a bit: Get a feeling for how each player on the opposing team behaves normally and under pressure, get an idea for their individual gimmicks (i.e. special weapons, positions or utility they like to play to catch you off-guard) and, if applicable, see what the team's game plan is. Then, you can come up with some counter-plays on the fly and see how they will react. Did they get caught off-guard for once, like you hoped? Did the opposing player predict your counter-play and counter-counter-played you? Did the entire team start playing differently, e.g. start rushing when they were previously pretty late-round heavy?
In my opinion, it's only when these small counter-plays start happening that CS truly comes to life. When a single flash thrown differently can take out the best player on the server and at least create some hope for a winnable round. When an change in strategy made on-the-fly can still salvage an otherwise unwinnable game.
With the shortened game length, I could perhaps see pro CS being played more statically, with a heavier focus on one-off gimmicks and reciting the thought-out strategy, because there simply wouldn't be enough time anymore to really comprened the game plan of each player and the opposing team as a whole.