It's an interesting point, but It's not like you need to use discord to setup a race, it's just about advertising to a larger group of people that you're interested in playing a multiplayer game, so they have an opportunity to join. Otherwise unless you have a large player base of people who are actively playing the game, at the same time as you, also wanting to play a multiplayer game, the odds of finding a match are quite small.

Out of curiosity, do you have any suggestions to improve the experience for low player base games?