I think it is no need to compare the current Barcelona with Barcelona managed by Koeman. Of course, it is so much different.
The current Barcelona managed by Xavi applies the nature of Barcelona tactics, tiki-taka. While in Koeman's era, he tried to avoid tiki-taka. Koeman tried to adopt Netherland national team tactics. But it totally failed because it wasn't suitable for Barcelona players' characteristics. After Xavi replaced Koeman, Barcelona returned to its nature, the players have good motivation to play again. So, they can play more aggressively and be stronger right now.
The tiki-taka strategy that Xavi always developed when he was at Barcelona is indeed very useful for breaking down defenses because it applies excellent teamwork and utilizes speed and accuracy to advance against until finally to the goal point will be executed to score goals. So far with that strategy they have always managed to break down the opponent's defense.
It will not work against a team that was fully defense. So many times this tactic gonna be useless against a team that has been putting whole of its effort to defend its field. This time so many team know so well how to prevent the tiki taka strategy like that especially for the big club. This club will always be so difficult when it was against a team that with fully defense like chelsea. In my opinion if strategy must be dynamic to follow what strategy that will be used by our opponents.