The problem is that not all strategies are equally, or even comparably, good on each board.
If I put my Gallery token on the only splitter on an engine boards, I get a +10 VP lead easily.
With Caves, the White option seems almost always better, because of how hard it is to keep our deck small.
Fork is probably okay on most boards, but there are always degenerate cases.
With prison, the Curse option seems better most of the time, and on boards where this isn't the case, Copper will be clearly better. I think it's hard to even find a board where this causes somewhat even chances.
Slums on a BM board gives a huge advantage to one player.
Cliffs could be okay, but I would still like it better as a shared resource where the VP go to the player who doesn't end the game.
Valley will also clearly favor one player on 90% of the boards where it is relevant.
The only way to use these is with tailored kingdoms IMO.