I just completed four OZ flights in the past two weeks, two of which were ex-ICN, all in Y. With respect to Y meals, there's not really any issue in my mind with the new catering. The meals were very similar to what they had before. A few differences was previously the chicken breast meal had a cream-colored creamy sauce, whereas now it's pinkish. I tasted very similar to me though. The potatoes in the past that came with that meal were always awful in my opinion, totally dry at tasteless, and I never ate any of them. This time they were actually all right and not as dry and had some taste. The exception was the cake with the new catering. It was hard and extremely dry, and not very edible in my mind. Yeah, I could have eaten it, but being so dry I didn't really want to. One other thing I noticed was that on one of the ex-ICN flights at the very edges of the chicken breast it looked like it might have been ever so slightly burned, I'm guessing due to either improper heating time in the plane's cooking system, or perhaps due to some change in the packaging material and some changes need to be made to how the meals are heated. The second ex-ICN flight didn't have that issue.
They are now using plastic cutlery on all flights in Y, or at least the flights I took. I don't recall that in the past, other than I think there was one destination where they used it but I don't remember which. But the last time I flew to/from LAX, I recall the cutlery being metal. I'm not sure if this change is related to the catering changes at ICN or not.
All the side dishes to the entrees looked normal as per what they've had all along, and on the LAX flight they came by mid-flight with a snack as per normal, but I was sleeping and didn't take it, so don't know exactly what it was.
The flight ICN-LAX was delayed slightly, and they gave the reason as "catering issues". Same for LAX-ICN. Seems that possibly because everyone knows they're having catering problems, they figured they might as well just use that as an excuse for any delays. I didn't think anything of it until that same excuse was given departing LAX, where I've never heard that excuse used before.
In summary, for Y, at least on the flights I took LAX and South East Asia, there doesn't seem to be any reason to avoid OZ due to catering issues.