This guy apparently had a chance to talk to a producer for 10 minutes at some event, and here's his story on the development of the game.
Here's a shortcut:
development started in 2013 (they acquired the licence quietly in 2010)
the 1st teaser took 4 months to make
during its development at that time, devs were pulled to work on Witcher 3, and the work on CP resumed in 2017
when the work resumed, came the "too many cooks" era - development was chaotic and all over the place. It was assumed that the game, at this pace, would be ready in 2024
suddenly, a prospect of a hostile takeover by Activision Blizzard scared the board. Secondly, they wanted to release the game in 2020, because it's iconic (which was probably an excuse to release it earlier)
a faster release would sooner increase the stock price, making the takeover less attractive
all of a sudden, the devs had 3 years to complete the game, instead of the 5-8 they thought they had
only 20% of the ideas made it into the game
the suits were breathing down their necks. most of the features never made it into the game, even with Phantom Liberty
Now, what was actually planned for the game:
10 romance options, instead of 4. 4 male only, 3 female only, and 3 who went both ways
Megablock 10 was supposed to be a mini-city, where you'd do most of your stuff
a metro system, replaced with a fast travel system
wallrunning
megatowers
many explorable buildings
a flying car
different type of clothing would give different bonus for various ocasions
The full story is in the picture attached.
So here it is - it all went to shit because the suits panicked.
Also, Activision-Blizzard really is an impressive company - not only do they destroy the IPs they own, but they also make other companies' games worse.