The absence of Spencer Reid, played by Matthew Gray Gubler, in the upcoming Criminal Minds season 16 has a good reason behind it. As one of the core agents, Reid had an awkward relationship with fellow FBI agent JJ after she confessed her love for him during a near-death experience, despite being married and having kids.
It's speculated that Reid left the BAU to distance himself from JJ for his own well-being. While Gubler may not return for this season, he expressed openness to future installments. However, the show will have to address how JJ and the team cope without Reid's intellectual capabilities and long-time friendship. Overall, it will be interesting to see how the revival handles Reid's absence.