I describe core strength as the ability to contract muscles of stability to protect joints and generate power. Core strength is not just about your trunk and spine. It includes your shoulders, your ankles, knees and hips and for some, even hand and fingers. Spinal and joint stability is one thing. They work in harmony together with your eyes, ears and breathing.

Every single athletic routine strengthens it. That can be a simple sit down to a chair, a sprinting drill, overhead squats, kettlebell swings, deadlifts, sparring against a fellow boxer, shooting a basketball, hiking or a simple belly breathing drill. Anything and everything.

After years and sometimes decades of sporting background, it is highly developed, even if we think it is not. Most overuse injuries are coming from overtraining, not enough rest, lack of sleep, lack of concentration, lack of mobility drills and so.
There are exceptions: medical cases for instance, where actual core strengthening routines can be prescribed as a way of improving posture and protection.

I am not suggesting here to eliminate core training routines, just to change ideology and focus on what is more important. For instance: I challenge anybody to do 10 x 1min front planks. It is hard, but most likely, even a teenager can do it. Try out different exercise routines and see how you feel doing the 10 x 1min afterwards. 5 x 3 heavy deadlifts / 3 x 80 bodyweight lunges / 15 x 200 on the track / 5minutes on the skipping rope / 1000m of swimming.
You will most likely fail in the plank routine, because your stabilising muscles are already fatigued. The intra-abdominal pressure you create, the torque caused by muscle tension around your joints, your breathing. They are all in harmony together with prime movers to create action.

What I advice is different than constant planks, isometric posture holds and Russian twists.
Learn how to move and perform all of your actions with the maximum rigour on form, posture and breathing. That includes your sport and your life. Do not make compromises on this ever !
Doing 100s of bodyweight squats with knees caving in, ankles pointing , back curved with a buttwink at the end is going to be problematic for landing after a jump, for forward propulsion and acceleration or even for a throw.
The same true to sitting all day long at a desk with hunched over back and neck fallen forwards, looking at the screen. Your gluts are permanently turned off. Your diaphragm is squeezed and difficult to use, you start mouth breathing using your chest and associated muscles, therefor intra-abdominal pressure is not practiced anymore on a constant basis. Your core is getting weaker and weaker, just by breathing improperly and not holding a correct posture.

Most athletes are tuned out of their body, so they would need a coach or anybody with a good eye for movement patterns. Weights should be often decreased or increased in some cases. Number of reps and sets decreased. Speed and pace dialled down. For a while till you have a "mind and body" experience, the only goal should be not breaking form. You practice your sport or movement. The very first sign of little misalignment should stop you. Have a break, a pause and come back later, the next day, the next time. We can see this in pro crossfit athletes. Instead of putting in monstrous 90minute workouts twice a day, they go with 10 - 15minutes, multiple times in 24hours (Warming up cooldown not included of course). Inbetween they stretch, they mobilise, they do little yoga and pilates. They practice breathing, they relax in a jacuzzi or hotpool and so.

Whatever you do in your day and in your sport practice will count towards core strength. Do not break form. There is no "run ugly". don't let your enthusiasm injure you. Your breathing timing is off by the 100s of a second ? Low back pain. You don't screw your ankles to the ground while lunging forward ? Knee and hip pain. Cannot squeeze and torque your ankles while farmer walking, aligning your knees, hips, spine, pulling back the shoulders in the socket ? Your throws will be off !

It is a complex system and while isolation drills can be an option to prime and pre-activate glued-down stuck structures as part of warming up, doing hours of isolated core routines day in day out is kind of waste of time. You should be practicing your sport !

Just don't break form !