This post makes no sense to me. How is the proposed solution where MITM attack could be going on the very first time I visit a website I want to trust a better

This post makes no sense to me. How is the proposed solution where MITM attack could be going on the very first time I visit a website I want to trust a better solution than the current state of PKI? The proposed solution demands that we trust the website on the first visit if the website behaves well. So now it is very easy for Mallory to perform MITM and behave well so that I trust Mallory's public key. Now Mallory can see all my traffic in subsequent visits. How can even one imagine that this is an acceptable solution?