Interesting post! I used to play poker professionally, and think that this post is correct in identifying limitations people assume poker is pedagogically valuable for (i.e., expected-value reasoning under uncertainty, and game theory) but misses what I think is most valuable about playing poker.

I feel fairly confident that within ~24 hours or so, I would be able to teach anyone enough strategy to, in principle, be a winning player who could maybe rack up $25 USD an hour at a typical US casino. But I don't think I could teach them the emotional control and discpline required to faithfully execute that strategy over a long period of time. That emotional control is what I see as the most difficult and generalisable aspect of the game. 

Many of what you listed as disadvantages of the game are actually the very reason why poker is so testing.

Most decisions don't give you feedback on whether you were right for the right reasons, right for the wrong reasons, wrong for the right reasons, or wrong for the wrong reasons.

Yes, and this is extremely frustrating. It's also pretty analogous to the hazy feedback you get in real life. (Maybe trading is different.) Learning how to discern between when you lost but made the right move, and won but made the wrong one, is a constant struggle. A common (bad) habit is to look at some seemingly objective source of information (e.g., a "solver" or simulations that try to find the nash equilibrium of a particular decision) — but this is almost always just an emotional cop-out. I think there are anologs to this in real life. A lazy example might be: "well the expert said to do X" when actually, if you'd properly evaluated X you would have noticed the expert was wrong. 

If your playing partners aren't sufficiently skilled at the game, you'll learn bad lessons.

This is a misconception.

Good players can make extraordinary profit against bad players, because their errors are highly predictable. Even the example you gave — of over-valuing red-cards — results in highly predictable mistakes (e.g., over-valuing random hands). Generally, the way you should think about playing against less experience players is just to account for the fact that they do random stuff, and there are better/worse strategies against random stuff.

But it is absolutely true that it people find it frustrating losing to players worse than them, in ways that feel unfair. Getting used to that is another skill, similar to the one described above, where you have to learn to feel reward when you make a positive EV decision, rather than when you win money. Again, I think there are analogies in real life where this thinking is valuable.

Players spend the supermajority of their time at the table not playing the game and not making decisions.

True, but again, this forces you to confront how to make good decisions even when:

• Bored.
• You've been losing for a while and this is the first opportunity you have to maybe win money.

Certain poker metaphors are perverse in real trading.

You listed a few examples:

• Bluffing
• Mixed strategies being at the heart of poker

I think the main thing that would generalise here is that bluffing is quite scary, and unpleasant, but it's still often the right move. It's really difficult to balance having the courage to do when profitable, without ending up being maniacal and doing it far too often. 

A separate rant on mixed strategies: Yes, these are at the heart of poker theory. But in practice, I think even at surprisingly high levels of play, people misunderstand on some fundamental level why mixed strategies are part of theoretically optimal play. Those reasons apply in vastly fewer situations than people realise. To be honest, this is a bit distinct/off-topic from the thesis I'm arguing for in this comment, but if I tried to tie it in, I guess there's some generalisable skill in not just mimicking theoretically optimal play without actually understanding what parts of theory apply in practice?

To sum up:

In general, all the above factors you've listed as negative are also some of the main challenges to playing poker well. I think that what I got the most value from in my time playing was all the repetitions of:

• Noticing a particular emotion or feeling, drawing me to a decision (e.g., "I'm scared --> fold" or "this guy has won the last five hands against me --> call")
• Identifying what parts of that emotion are actually valuable and informative — just ignoring emotion is a mistake, it usually contains important information. The skill is disentangling what parts of the emotion you endorse versus which parts are irrational.
• Once you decide on what the best decision is, actually clicking the button. It's shocking how hard that is. (A funny example here is from one of the most famous poker players' "highlights" including repeatedly, correctly, identifying the specific hand his opponent has, and calling anyway. ^[1])

There is one part of what you're saying that rings true to me:

It takes too long to get good enough to squeeze the real educational juice out of the game.

Yep — and for this reason alone, I'd be reluctant to recommend anyone play poker for "epistemic training" reasons. Play poker if you find it fun, and gamble responsibly! Even though I'm arguing above that there are valuable lessons in poker that do generalise to real life, I spent thousands of hours playing, and it's honestly still a kind of novel rarity to go "oh there's something I learned from poker that can help me here." Most of what you'll get from playing poker is getting good at poker.

1. ^{^}

   Though, it might have been the right play if he was sufficiently uncertain! That's the frustrating thing about the game :).

I think it's possible the competence of government in a given domain is fairly arbitrary/contingent (with its difficulty being a factor among many others). If true, instead of looking at domains similar to AGI-risk as a reference class, it'd be better to analyse which factors tend to make government more/less competent in general, and use that to inform policy development/advocacy addressing AGI risk.