The clarinet is quiet easy to learn and understand, it is a lot easier than some wood wind instruments like the oboe and the flute. The clarinet requires less air pressure compared to the flute. Clarinet is a single reed instrument which is easier to maneuver compared to the oboe which is a double reed instrument which is more complex. They are more intricating musical instruments than the clarinet, examples are: French horn, violin, piano and a lot more.
However, it takes hard work to gain mastery in playing the clarinet but with time all the skills can be acquired and it is not as complex as many other musical instruments.
This is a loaded question, one that can mean many things. Regardless of what is meant, no the clarinet is not the most intricate, nor the most difficult to learn. Instruments that could be considered more intricate based on the complexity of the physical structure would include the piano, the sitar, or Uilleann pipes. If the question is about how difficult the clarinet is to play, compared to other instruments it is quite easy.
The oboe, French horn, bagpipes, and organ are all far more difficult to master. Although the clarinet is not all that complex or difficult to learn to play, it is a good starting point for a young player to learn correct embouchure, music reading, and the hand-eye coordination needed.