In the video attached below, Coach Eric and Coach Stephane dispel the ridiculous notion that you can't get strong doing CrossFit.
CrossFit defines strength as the productive application of force.
The two break this down into three things: an athlete's contractile potential, their ability to utilize the nervous system and recruit motor units within different muscle groups to work together quickly, and technique or how efficiently they can use their potential.
Who is Eric and Stephane? They are two of the top CrossFit coaches in the world. They have worked on the CrossFit Seminar Team, Eric currently still does. They are both employed on the CrossFit Education team to provide knowledge to all CrossFit coaches and athletes around the world. Stephane is also a Collegiate Strength and Conditioning Coach.
In the simplest way, they know the methodology of CrossFit and how to apply it at it's highest level.
https://www.youtube.com/watch?v=qimI_SVJrcM
Here is an additional article for you to read on building strength in a CrossFit gym.
Respectfully,
Josh Melendez