What are the limitations of a simple PKI?

A simple Public Key Infrastructure (PKI) is limited by its reliance on a single Certificate Authority (CA), which can create a single point of failure and potential security risks if compromised. Additionally, it may lack scalability and flexibility, making it challenging to manage large numbers of certificates or diverse user needs. Furthermore, simple PKIs often do not provide advanced features like revocation mechanisms or auditing, which are essential for maintaining trust and integrity in a more complex environment.