Blame CBTC on those issues as well as other Line issues..
Again if you saw how difficult it is just to get into Queens Plaza on D2 track or Vice versa from the you'd sing a different tune. Take it from a line TO who has done it a few times. CBTC changes everything.
Well you got until 2026 that's the Scheduled completion of the work in Queens that's why there are delays i wont get into the Work Zones(9 mph tops) that these trains have to go through.
The 179 service will most likely be the service thats Cut hence the extra trains used for service.