I think that this question is impossible to answer with one particular perspective. As an INTJ-A and a big fan of type-casting and in general (algorithms), I’ll share my perspective:
I (believe/think/feel/suspect) that INTJ’s are best at spending years or decades collecting seemingly unconnected bits of information that is combined with knowledge acquired through reading, self-designed experiments, and observations. Along the way, life circumstances specific to each one begin to emerge from a collection of experiences or a few compelling ones. Once a purpose of life is identified and refined through the years into a vision, or if a mission presents itself that aligns with the vision, they can take that cumulative understanding and apply with persistence, resulting in a high rate of successful outcomes relative to the intended goal.
To summarize, I think INTJ’s are best at perceiving a potential pattern which they then seek to understand and reverse engineer, followed by applying and refining. They realize that this is just one of many and that they are all connected and meshed by forces unknown to them, but that clearly exist. Spending a lifetime seeking to understand this backbone interconnection that governs what appears to render us without willpower or limited control at best; once they find a purpose, it is very probable that they can achieve it given that the focus of life is in understanding its source code.