While I'm not a fan of crypto backdoors - thinking of it, aren't all public/private key pair systems a form of backdoor? If someone leaks the private key then e

While I'm not a fan of crypto backdoors - thinking of it, aren't all public/private key pair systems a form of backdoor? If someone leaks the private key then everybody with the public key are affected? Think root CAs or app store signatures as example. They manage to keep their private keys secret quite well.