The changes that were made to the Mario Party formula in 9 aren't as bad as people make them out to be. The series had been in a downward spiral in quality since the Gamecube and the games had just become more boring with each new release.
I see a lot of complaints about "putting all the players in the same car". While I can see the point that it goes against what people were expecting from Mario Party, gameplay wise it's actually much better.
Play any of the games between 5 and 8 with friends and tell me if they're still fun. The board is so large and there are so many branching paths that even if you're playing with someone else you're never going to cross each other, the only times you're actually playing multiplayer is during the minigames. Even powerups that are supposed to make you interact with others become completely pointless.
With all the players in the same car you can actually fuck over the other players depending on your dice rolls every single turn, and since the boards are now more linear and have progression, you just don't keep wandering about the same spots over and over.
Mario Party 9 is miles ahead any of the other games from the series since it started going downhill and nobody will even give it a chance because they don't like change.