Re: are power cleans useful for the majority of lifters?
There's no set number of pounds you have to clean to get a benefit from the movement--if you're power cleaning 155lbs or 175lbs, you're able to generate more force and explosiveness and demonstrate better neuromuscular efficiency than someone who can power clean 135lbs. Obviously 225lbs would be better, just like it's better to squat 350lbs than it is to squat 300lbs, but any improvement helps.
Aside from the KB swing, the power clean is the easiest dynamic hip extension movement to teach--that's why they're included in SS alongside the basics like squats and deads. If you had continued pain from doing them and your form was ok you're probably dealing with some mobility issues, and it would make more sense to address them rather than ditch power cleans.