I've just caught up with the discussions here and actually I am quite surprised that many people think that it's all arm. I don't know whether my surprise is a by-product of the fact that I've had some coaching before, but it does surprise me there are people who don't think legs or other parts of the body are involved in a hit. Like Carl said, I've been finding shadowplay training really helpful to get my mind back into that coordinated state rather than simply being lazy.
I wonder why people think legs don't come into it though. Even when you watch some of the big players, I believe one of the replies mentioned people idolising Xu Xin, you can quite clearly see the leg and weight transfer at work. Well, at least for me that is. Sure he has a long loop arm, but he throws his weight very noticeably too.
I wonder if the reason why some reviews claim certain rubbers are slow because they are playing with just their arms.
From my experience, most players and coaches do think that using the legs is important. There's a lot of talk about weight transfer. But there seems to be some confusion as to how it's done and over emphasis that one should "use" the wrist, forearm etc. Maybe it's just a language problem and I've been misinterpreting. Maybe they assume that because they are using their legs properly that the player they're trying to help is doing the same. Or in some cases, maybe they're not seeing it?
Even when I knew what to do and saw myself on video, I still couldn't figure out many things until quite recently. It's possible, for example, to be rotating your waist without using your legs and you can still get good power and spin that way. But I think it's even more efficient to be using your dominant leg to push the ground to drive the rotation. It's a very subtle distinction. It's also not just pushing with the legs, on most shots you need to also fold your torso/bend at the hip (more so against heavy backspin).
In this video I'm trying to push with my dominant leg, using mostly my quad and glute to push off and put my body into rotation:
In this video I'm mostly rotating my waist and not pushing the ground:
Unfortunately you can't see my feet much, maybe you can still see it? Since changing my focus to the technique in the first video (pushing with my dominant leg), my FH has become more stable and efficient. I've been making some more small adjustments since then.
I think quite a few coaches coach the arm structure of the shots rather than how to get the arm moving efficiently by using the body. When a coach now tells me to "use more wrist" I instead think they mean to let my arm backswing in such a way that will get my wrist moving more on the forward swing. I used to think that I was supposed to consciously whip my wrist or when told to use more forearm to tense my forearm muscles.
In the right context this advice can be helpful, but it can be difficult sometimes if you're inclined to take the advice literally like I often did.
Brett Clarke helped me realize much of this and a lot of practice, shadow play and visualization helped my technique tremendously. I recommend checking his work out, he's truly a world class coach.