While it is not officially explained, there seems to be very strong evidence to suggest that to hit someone with a natural-type Devil Fruit requires being able to hear the Sound of Life, since Rayleigh can slice through pure light and as far as I know light doesn't have a counter element (Darkness is already taken by Blackbeard). This seems to be exchanging one absurdity for another. For about 50 volumes we basically are told people who are of natural type are more or less invinicible (there just isn't that many counter elements around... note that the heat from lightning would've been enough to melt rubber anyway). Now with Rayleigh showing up, apparently everyone's been doing it wrong. As long as you can hear the Sound of Life you can hit through light, ice, fire, darkness, or anything else for that matter. It'd look like the sound concept can be specialized. I'm guessing one of the new guys that have no devil fruit power and can hurt Luffy with just punching must be able to hear the Sound of Rubber, but obviously all the people at the top of OP should be able to hear the Sound of Life, which encompasses everything.
So for example the ice Admiral could've died 4 times already just in the fight against the Straw Hats. If anybody on the Straw Hats team could've heard of the Sound of Life (or even just the Sound of Ice) then any of the wound he took would've been fatal. The light Admiral basically got blown to smithereens and glued himself back together. Again if any of his attackers can hear the Sound of Light, then he would be dead! The most powerful force of justice could've been trivially defeated by anybody if they can only hear the respective element they belong to!
I know the author of OP doesn't seem to be particularly good at coming up with a good worldview, but going from natural = invinicible to sound of life = invinicible seems to be a step backward. Now every fight in the future, you'd have to always wonder what if the other guy can hear the Sound of Rubber or the Sound of (insert devil fruit here). And really if OP is to fight without these whacky rubber and other devil fruit abilities, it'd really not be that great.
So for example the ice Admiral could've died 4 times already just in the fight against the Straw Hats. If anybody on the Straw Hats team could've heard of the Sound of Life (or even just the Sound of Ice) then any of the wound he took would've been fatal. The light Admiral basically got blown to smithereens and glued himself back together. Again if any of his attackers can hear the Sound of Light, then he would be dead! The most powerful force of justice could've been trivially defeated by anybody if they can only hear the respective element they belong to!
I know the author of OP doesn't seem to be particularly good at coming up with a good worldview, but going from natural = invinicible to sound of life = invinicible seems to be a step backward. Now every fight in the future, you'd have to always wonder what if the other guy can hear the Sound of Rubber or the Sound of (insert devil fruit here). And really if OP is to fight without these whacky rubber and other devil fruit abilities, it'd really not be that great.