Admittedly, if you are to specialize in either performance or aesthetics, then yes, you'd need to add specialized exercises into your regime. Specialized exercises are things that gives a few benefits and minimal carryovers to other things, but you do it anyway because they help you achieve your goals. Bicep curls grows your biceps and strengthens your elbow joint, which is why they are used by bodybuilders and some powerlifters. Agility ladders trains your coordination and ability to move in stop-and-go patterns, used by athletes that needs to perform well with those movements. Isolation machines, cable machine exercises, etc. falls under the domains of specialized exercises as well. They are things that are AWAY from the compound lifts or calisthenic movements, and focuses on either practice of a certain movement pattern, or emphasizes on strengthening a focused group of muscles. Exercises such the deadlift are NOT specialized exercises, and have so much benefits and carryovers it will not be covered under the context of this article. 


Bodybuilders (aesthetics goal) need to isolate because they carry so little fat that they're literally sculpting their bodies. Like an artist, a difference of a centimeter in the circumference of their arms/legs/midsection can make the difference between winning first, or placing second in a contest - that is how lean they are. We only need to worry about this amount of detail if we're already rocking at least a six pack abs. 


Badminton players (performance goals) need to incorporate skill work - but they're competing in a particular set of sports with a particular set of skills. They may be doing agility ladders but that's for them to train the ability to quickly change their movement patterns on the floor with an opponent - what use is there to us average joes trying to get in better shape? Not much. If we wanted cardio, we'd be better off doing hill sprints. In exercise selection we want the most benefits and carryovers from one exercise as we can get aside from just the idea that is 'fun' or 'something different from the usual'. We want the most cost & time-effective exercise there is, so that you can do it more often over less time, to make your body adapt to it (which comes with all the plethora of benefits such as increased fat loss, muscles and strength, all the good stuff).