I don’t think anyone actually uses kettlebells as the sole lift for a session though and expects athletic wonders to happen at the top level.
When being used in a program of just swings, turkish get ups, goblet squats, etc, it is a great means to get someone that is new to lifting in shape using more athletic movements that aren’t as intimidating as olympic lifts, barbell squats, etc.
I find they they are a great way to improve stiffness and you are able to create a large eccentric overload through the posterior by actively hiking it backward on the downswing. The posterior stretch at the bottom and then the hip pop at the top after the the pullthrough is absolutely a great way to increase power, imo. I use them as a plyometric alternative on days that have had higher speed volumes or when coordination seems to be a bit lower than usual so I can still work that quick eccentric ability a little extra.
It’s simply a tool that can be used in certain situations. Nobody buys a hammer and declares “Now I can build a house!” But the tool affords extra options for situations where maybe an olympic lift or a plyo isn’t exactly the best option.