As for how close Stockfish 8 is to a current version of Stockfish, Stockfish 15 has ~400 more ELO than Stockfish 8 as measured in their own self-tests[4].
However, when making these comparisons between AlphaZero and Stockfish it might be tempting to frame it as machine-learning-engine vs classical-engine, which is not true. Stockfish incorporates a neural network when evaluating chess positions[5].
[1]: https://en.wikipedia.org/wiki/Top_Chess_Engine_Championship#...
[2]: https://en.wikipedia.org/wiki/Stockfish_(chess)#Top_Chess_En...
[3]: https://en.wikipedia.org/wiki/Leela_Chess_Zero
[4]: https://github.com/glinscott/fishtest/wiki/Regression-Tests#...
[5]: https://stockfishchess.org/blog/2020/introducing-nnue-evalua...
[1] https://www.youtube.com/watch?v=N2MncpRMnFA&feature=youtu.be...
Think of the amount of complex computation must be happening for an elite gymnast for example. Sure, they aren't solving the equations consciously but at some level computation is happening - or even something as simple as making sense of all of the individual photons arriving at the eye. The subconscious is what I am suggesting we try to exploit. Even then, it seems likely that a "special" brain would be needed - hence why large numbers would be required in order to find it.
By that logic, my cat should be trainable to a Chess Grandmaster level because she performs complex computation as she navigates my backyard.
>The subconscious is what I am suggesting we try to exploit.
Is there any evidence that a subconscious is exploitable it that way ... at all. Because learning doesn't work that way - especially for higher-order knowledge like Chess.
"Probably not" indeed. Human brains need to be stimulated in order for them to build their neural net. Blindly following instruction is not stimulating.
>but our current approach (studying openings, etc.) is obviously not working
That's part of the current approach, not the full approach. Kids that show promise in Chess, already train with computers today (in addition to personalized coaching, and strategy study). I have no doubt that the current generation of chess players is best of all time, and that the next generation will be even better. Even with that, I don't think any human will be able to train enough to beat even Stockfish, much less Alpha Zero - just as no human will ever train enough to beat computers at arithmetic.