In my opinion all the extreme hate comes from exaggerated expectations that people created during the 18 years.
It's fine to have high expectations, but they should always remain realistic, otherwise you're simply naive and delusional.
Things were pretty clear since the beginning of the kickstarter, still people didn't want to understand that a crowdfunded game can't have the same production values of a AAA or AA game from a big publisher.
Especially in this case, the first two Shenmue weren't simple games, they were two of the most beautiful game of all time, made by one of the best team ever, and basically they created a new genre and models for game design that are still followed and used 20 years later...
Probably no current software house could replicate the same earthquake that was Shenmue in 1999 (even Zelda or RDR2 are no match), and surely you can't do it with spare changes from a crowdfunding campaign...
We are extremely lucky that Shenmue 3 was a real Shenmue game, because we really risked to have a mobile game.
If more people understood this back then, we would not have other "shenmue fans" who spent lots of money without understanding what they were backing, and now wishing for the death of the franchise on basically every forum on the net, hindering our already small chances to see Shenmue 4.