Yep, that's exactly what I came here to say. I was hearing him describe the Dunning-Kruger effect. It's like we have three classes of investors: As, Bs, and Cs.
Investor A thinks he's a B. B thinks he's a C. And the C think's he's an A.
You might think this is only a problem for the C. But it's actually a problem for all three of them. They're all failing to estimate their own ability and it negatively affects the outcome.
I like to think I am less susceptible to the Dunning-Kruger effect because I am not hyper-intelligent or extremely unintelligent. Maybe that is just a manifestation of the effect! Maybe it is not? Damn. See what I mean?
Also, it seems reasonable that certain people (perhaps myself included, although that is not altogether self-evident) may be technically capable of "mastering" a domain, but also understand their own limitations and therefore choose not to spend their limited mental capital on that domain while still participating in it at a lower level simply to increase the list of trades they are a jack of in order to be able to come closer to mastering another trade, or at least being a better jack at a particular trade. Wow, what a sentence.
Finally, as relates to almost completely off topic, that this post could be rewritten replacing investing with philosophy, theology, politics, etc., and that it would be prudent for those that agree with the assumptions of the article to apply them to these parts of their lives as well.
I have for quite some time been part of the sheep mentality to crypto (being new to this space), but finally have found the benefit of doing my own research. In fact for the first time this has shown in the (slow) growth of the value of my portfolio.
However I have certainly found that in forums certainly individuals match precisely the definition you provide. To someone like me, this is perceived as arrogance and I have to resist the urge to go back to old posts and point this out when their decisions/advice has been shown to be flawed or totally wrong.
This certainly is even more true in the crypto world where in the short term, peoples emotions seem to dictate price as opposed to well thought out technical analysis (this of course is a generalization).