Basically, train really strong AI players using the AlphaZero method with the rules of the game changed by a human author (either some variant of Go, or a completely new game). Then take a look at the games the AI plays at its strongest level and let people decide if the game looks interesting enough for them to try play competitively. With the strong AI player already in place, human players would have something to learn from and a serious competitive culture could be born.
In the absence of something like this, I don't think it's surprising the only popular ASGs are very, very old. Modern commercial board games are fine, but they supply a different demand than ASGs.