While I do agree that if the hardware was still in a state of flux, finishing drivers would have been very hard. Even more so if some feature the hardware designers had promised didn't work or was pulled at the last minute.Both the hardware and the drivers base on the iGPUs which exist for well over a decade already. Improving the drivers is something Intel could have done starting from the announcement. At first the opposite happened instead.
However, there must be things which can be abstracted and done beforehand. Maybe even only basic things like analysing the actual shader code of the top 100 games, or starting a shader recompile project, or plenty of other things.
Its those kind of things the driver teams should have been doing while the new hardware was being designed.