Starting an exchange may only be max. 5% of the success. The people to trade on this exchange, these are the most difficult task. Especially today where there are so many competitors with good service
I do agree, although if you don't have anything to get people onto, this is a problem too. I actually share some ideas in "How to Stand Out" chapter, but it's up to the entrepreneur to find creative ways to attract customers.
Normally, however, it's "business as usual": buying leads on Facebook and Google Ads and making sure the cost is less than CLTV (customer lifetime value) or something to that extent.