I've also heard rumors that AlphaStar (https://deepmind.com/blog/article/alphastar-mastering-real-t...) was essentially put on hold because it was too expensive to improve/train. The bot wasn't able to beat StarCraft champions and _only_ got to a grandmaster level.
(Sure, u need to somehow roll forward and rollback the StarCraft world, but for Atari using MCTS was shown to be an order of magnitude more efficient )
I have also seen comments that the search width is too large, or maybe academic purity consideration?
At the last Blizzcon they had it around. The setup wasn't ideal, so Serral (won world finals in 2018, reached semifinals in 2019) wasn't really happy with how he played, but it won
This was also a version where they'd worked on preventing its ability to micro at quadruple digit apm
I'd even argue that they missed their goal by a long shot if their system isn't able to play arbitrary maps - every human player can do that no problem.
Still what they have accomplished is a miracle.
https://storage.googleapis.com/deepmind-media/research/alpha...