So? Darling is 9 years into its[1] development and hasn't really reached the maturity that Wine had after 7 years of development.
If memory serves me correctly[2], I'm quite sure that I played one or two Directx games on Linux using Wine in Dec-1998 - that's 5 years of development.
Fair enough, most of the games/apps did not run (Dune 2k was listed as "working" so I ran out and bought a copy only to find that it got no further than the game menu screen) but it ran more Windowed programs and full-screen games back then than Darling does now, so I don't think that I am performing an unfair comparison in that regard.
It might be that there is just not enough contributors to Darling to proceed at the pace that Wine did.
[1] I don't believe an apostrophe goes between the 't' and the 's'.
[2] At this stage of my life I treat my memory as a rough guide to past events, not as a record of what happened, so I could be wrong about the dates towards the end of the 90s.