Workplace loneliness is a real problem. For 45 hours a week I feel isolated

> One expert advises breaking the ice each morning with a “Hi!”, as if that is a relationship builder, rather than something done by all but the most sociopathic.

Exactly. Starting a casual chat with strangers (or half-strangers that happen to be colleagues) is not an easy thing for an introvert, who to have a chat needs to have a topic to talk about, otherwise he stays silent. It's a chicken-and-egg problem: no common topic leads to no chat, which leads to not getting to know those strangers, which leads back to no common topic with them.

Simple "hi" is not nearly enough to have a chat. It is a first step, but there are dozens following that are still needed. It's like saying that writing a sentence leads to a writing book. It's necessary, but it's not enough on its own.