Sports specific training has been around for a while now and promises to get an athlete better at their sport by training the positions and actions that they will use in games. While this sounds like a great idea at first, the extent to which it has been taken has reasons to cause concern, as many gyms and fancy equipment merely mimic the sport action, but just add some form of weight or resistance to it. This is all based on the SAID (specific adaptations to imposed demands) principle, or more commonly called the principle of specificity, which shows that we only adapt to the things that we are exposed to.
However, many of the people pushing sports specific training are there to develop physical capacities, not sports skills and tactical training. Because of this, what is taught during these training sessions may contradict what the athletes sport coach may want. Also, if too much resistance is added, then this can alter the biomechanics of the movement and can ultimately interfere with the learning process and prove to set the athlete back instead of making them better.
To add to this, many of the methods used in sports specific training are primarily focused on moving fast and developing power. While power development should be part of every athlete's strength program, without a sufficient base of strength the athlete will not adapt as well to the power training and will be leaving some chips on the table. In fact, general strength training can raise an athlete's power to a greater extent than just power training, until the athlete has reached sufficient maximal strength levels.
This shows that general preparation is the foundation for specific adaptations. Without this foundation of sound movement skills and strength, the athlete may be at an increased risk of injury. And on the flip side of that, by only training "sports specifically", you put the athlete at risk of overuse injuries by only working through the same motor patterns that they use all the time in competition.
Ultimately, a trainer or performance coach is there to develop the physical capacities so the athlete can be more successful in their sport, not just add weights while blindly thinking that it will transfer better to competition. At the present, the best form of sports specific training is a holistic program that gets an athlete stronger, faster, and more powerful, while minimizing the risk of injuries that could possibly occur from overuse. Outside of this, skill development should be left to the sport coaches to build on top of the general prep that has been done in the gym.