When I design a game, the first thing I consider is if I will enjoy playing it.
A lot of work will go into a game before it’s ready for the world, and you are unlikely to craft something significant if you don’t care deeply about it.
Building a game that you want to play is going to give an immediate avenue into caring. If you want to play it, you’ll want it to be good.
It also gives you confirmation that there must be some market, and that this market will enjoy the game. You cannot be sure of the size of this market, as it’s defined as people who are like you, but it’s sure to be more than one.
You are unlikely to get rich creating boardgames. Make something you love and will have fun with, and you know you’ve spent your time well.