Understanding the root causes

So, how do we avoid repeating the same mistakes? Are these vulnerabilities and security threats an intrinsic part of the internet that we cannot counteract, and therefore we do not even try? Or are there methods that can be used to significantly improve the security in communication?

The major problem was that solutions were devised before the whole problem was understood. They wanted to find a method to transmit messages between computers in interconnected networks. They managed to do that exceedingly well. They did not consider, however, how to avoid the injection of fraudulent messages, or eavesdropping on transmitted messages. So, these were left out in the underlying protocols. As it became evident that these problems existed and posed a threat, solutions were added to solve them. But as these were aggregates, they became optional additions. They were never integrated into existing technology and made mandatory, since that would break compatibility. And...