I’ve been following their MMM warmup and matches and I think the result (10-0 black ) really underlines how difficult the matchup is for blue.
I take the point of it being an expansion, but some non-zero (albeit small) number of people will end up receiving it as a gift from someone who doesn’t know any better or maybe they just really like blue and black in magic and want to start with their favourite colours (even if blue in codex is quite different from blue in magic).
One of the goals of codex was to make a game where you wouldn’t lose before you started playing. As far as I can tell from the data if you are blue P2 and your opponent is black you may as well concede right there, and its not much better for P1 blue. If this was some multicolour deck that had these issues I’d be a lot less worried, but the fact that its between two mono colour sets which are actively distributed together makes it seem much worse.
Now obviously there is still a lot to love about codex and the result will be that blue continues to be avoided in tournament outside of strong multicolour combos. However I definitely think the game needs, no deserves a fix for this problem.