It’s a feeling someone has and the way every person is accustomed to. Most of the tefillos in my life took place at minyanim going fast (to very fast) and i usually finish way after the minyan does. Davening should be about connecting and talking (for real) to Hashem not just Lip-Service (pun intended). There are many people that say every word with its right pronunciation and all but are they really having concentration???
Besides, would they talk that fast if they were giving a presentation or even talkin to a friend???