Blame is too laden a word here.
TL;DR: CDPR have opted to shutter their in-house engine, Red Engine (which CP2077 was built on) in favour of a partnership with Unreal. Most of their devs have now switched to Unreal; with only those left on the upcoming CP2077 release still using Red Engine 4.
They have opted to no longer work at all on the Red Engine projects; ergo they either port CP to Unreal (an incomprehensibly large task given that Unreal doesn’t support many features that Red does, or at least not in the way Red does - not a slight on Unreal, simple reality of different engines, especially internal vs external tooling), or cease further development of CP. They opted for the latter.
I’m employed in Film and currently “stood down” while our actors are on strike. On one hand it’s great to have time to hit some of the games I’ve been hoarding, on the other, I may be playing them in a cardboard box come February.