Many strength coaches have a set of major lifts, and traditional accompanying lifts, that they utilize with all of their athletes. If a kid isn't good at say, squatting, they work on the squat by squatting more often, sometimes with coaching cues to help improve the movement. On the other hand, some coaches take a kid who doesn't squat well, stop him from squatting all together, use a substitute exercise he can do well, and work on his restrictions separate from the lift. What approach do we take?
We'll use the squat example - let's say a kid squats, and his right knee kicks inwards a little bit as he goes down. His heel then turns in, the weight transfers to the inside of the foot, he twists slightly and shifts slightly to compensate. If you're not looking carefully, you probably wouldn't notice. What does this athlete need? More practice squatting, or more work on his biomechanical integrity?
The first thing we do is check for proper movement ability - in some cases, the athlete just doesn't yet know how to do the movement, and with a little bit of practice and coaching he can do it just fine. We'll identify those kids during our analysis, and coach them properly before they load, then get them into the lift.
More commonly, the athlete has a restriction, whether in mobility or stability, that prevents them from doing the movement properly even with a bit of coaching. This is the important case - the athlete's knee, heel, and hips are compensating as noted before, and it's due to a restriction in the glutes and ankles - what do we do?
We regress the movement - that is, we don't do the squat just yet. Think about it - if a kid is compensating during his squat, and he has a restriction that can't be fixed quickly through a few coaching cues, what does squatting through the mistake accomplish? It forces the athlete into a position his body has said it is not ready to handle. It's putting excess force on different areas that are forced to pick up the slack for the restricted portion. And, it's leading to potential overuse injuries, whether in the weight room or when he eventually hits the field. All those non-contact injuries we see when an athlete plants wrong and all of sudden his knee gives out? Some are unfortunate, but others are avoidable by not forcing the body to wrongly compensate in the weight room. When certain areas are forced to compensate, and we reinforce poor movement patterns, we create a path for injury in non-contact situations.
What we need to do is:
a) Take them off of that lift (in this case, a squat)
b) Substitute something that they can do properly and still put load to increase strength and power (say, a reverse lunge, an exercise that is a bit easier to execute properly, and can still be loaded for big gains)
c) Identify why the athlete has a restriction (let's pretend in this case it's because he struggles to properly use his glute medius, and therefore puts extra stress on the knee in a valgus position)
d) Address the restriction and create stability and mobility (for a glute medius issue, we might work some mini-band activations, unweighted assisted squats with lateral activation, supine and prone squat variations, perhaps even some stretches, etc)
Once we've done that, which can take anywhere from days to years, we can return to the squat, having fixed the movement pattern and still gained strength using our substitute exercises. We've decreased the risk of injury, including risks from lifting wrong, risks from enabling compensation when we hit the field of play, and risks from long term overuse.
A good analogy for this is a math teacher going over long division. If little Johnny comes up to the teacher and says "Mr. Jones, I don't get long division, none of my answers are right, can you help me?" should Mr. Jones just offer another worksheet of long division problems and tell him to go work it out? Or, should he break down the problems, identify what Johnny is doing wrong, address those issues specifically, then return to the long division worksheet? The teacher who just hands out additional sheets to kids that are struggling is lazy - he's not actually teaching, he's just pushing. The teacher who takes the time to actually teach Johnny how to do it properly is doing his job. The same goes for strength coaches - marrying your athletes to your favorite few exercises is lazy. There are websites and apps out there that can do that. A good coach will take the time to understand the athlete and choose the exercises that are best for him or her at that time, and work them towards the more advanced lifts with proper coaching and programming.
I feel obligated to say there's nothing wrong with loving or preferring certain exercises - I have my own preferences when given the options. There's something wrong with thinking your favorite exercises are right for all populations at all times, and falling more in love with your exercises than you do with the improvement of your athletes. No single exercise is a cure-all for everybody. Each athlete requires time and coaching, and when they are ready for your favorite lifts, get after it! But until then, address the causes for WHY they are doing things wrong, instead of figuring that the symptoms of restrictions will work themselves out during compensated and loaded repetitions.