Current systems prevent most abuses, and many people are working on improving it to prevent more abuses.
As an excellent example, Certificate Transparency has almost completely mitigated the potential abuse of compromising a certificate authority and using it to MITM traffic. Similarly, "binary transparency" or "software transparency" will hopefully eliminate the abuse of delivering a "special binary" to just one person that others have not received.
Part of the threat model is the belief that any system with a backdoor has any hope of "preventing abuses". The backdoor is the abuse, leaving aside all the misuses of it that will happen.
As an excellent example, Certificate Transparency has almost completely mitigated the potential abuse of compromising a certificate authority and using it to MITM traffic. Similarly, "binary transparency" or "software transparency" will hopefully eliminate the abuse of delivering a "special binary" to just one person that others have not received.
Part of the threat model is the belief that any system with a backdoor has any hope of "preventing abuses". The backdoor is the abuse, leaving aside all the misuses of it that will happen.