Only tangentially related, but I think the mid/late game is a much more interesting/useful/hard avenue for chess tools.
Chess.com's opening explorer is pretty good, which it seems like this is kind of trying to compete against.
What I struggle with is the post game review, where I make a dubious move but I don't actually understand the reason why it's bad. Sure, the engine shows better moves and the refutation to my move, but I often don't know why. The automatically generated explanation is usually pretty poor.
I wish I had even a poor copy of Danya giving me commentary.
Perhaps I should just lean in and try to implement something like this, but focus it more on coaching than commentary.