Yep, you sure derped. Tell you what....cut off the first knuckle of every finger, including your thumb, and from every toe, including the big toe. Let us know how well you adjust.
Look at your hands and visualize them without the tips down to your first knuckle. If you can't see how, while severely limited, you can still adapt and continue to manipulate objects - even use a pen - with your hands, well... you didn't think your comment through and did a fire from the hip derp .
Removing a cat's claws fundamentally eliminates its ability to perform many functions that are feline. A human will likely adapt better to the loss of their finger tips and managing to continue to perform their day to day functions than a cat will to the loss of its claws. A human will actually manage to learn to do many of them, albeit with limited function, while a cat can no longer do them at all; ignoring all the functions of an outdoor cat that become impossible - indoors they can't climb any more for one.
As far as feet, people can and do learn to walk with the loss of toes, including the hallux. I work in medicine and have seen that particular injury first hand. Humans adapt very well to injuries if they put forth an effort. As far as drawing a comparison of removing the tips of all your toes, consider not needing to balance yourself on your two feet and walking on all fours, as well as having a tail with the primary purpose of balance. I mean, really, is the fail this strong ? They're a different species and the analogy is meant to give human context to illuminate that you are crippling the animal when you declaw it. Since they don't roll over and die afterwards and continue to eat and defecate all is well ?
Claws to a cat are a lot more than climbing curtains and scratching furniture, those are just the things that annoy owners. All the other activities they use them for that don't cause a nuisance are important. They are as vital and intrinsic to how they live as the tips of our fingers are to us. Removing them is cruel and selfish. Rather than dismember a cat, why not get a different pet if you can't tolerate cat behaviour or put forth an effort to curtail it ? Effort being that if you take the time when they're kittens you can train a cat not to scratch furniture, not to see hands as toys and to trust humans.