Well, I think the piece by piece acts as a nice bridge right now between the familiar way how previous RCT games worked (since many people here like to refer to them as the baseline for this) and how it could work in the future. I never stated that piece by piece was far superior to anything that may or may not exist now or in the future. Like with everything, it cal always be improved upon. There are no such thing as a perfect anything in the world. But, for the current version and limitations of Planet Coaster you won't see the piece by piece building part go away. You can still add this spline tool for certain items like fencing to improve the placement of those. It also works very well for standard, smaller buildings where you don't need or want a lot of complexity.
Some people may always want to prefer piece by piece in the way it is now because it is familiar and they work faster that way or be more comfortable. No different really than that some companies still design all their stuff (being parts, houses etc.) in 2D applications and some do the same in full 3D. I think a lot can be improved in the building system but the choice to stay with what made this genera great in the first place was a solid decision at the time. It probably also solidified even further after the first development diary came out and everyone was in aww for the grid based building system. If everyone hated the system or wanted something else, that would have been the time to say so, not now. Who knows, maybe they would have redesigned the system. We are long past that point now.