I worked for two startups and they BOTH wanted to build marketplaces. One of them had amazing traction with sellers because they said "it's free to sell right

I worked for two startups and they BOTH wanted to build marketplaces. One of them had amazing traction with sellers because they said "it's free to sell right now, hop on in!" They failed because they didn't have customers. The other one was an advertising platform, but they didn't have enough advertisers to actually PROFIT from selling their advertising. So they sold lots of advertising... only to pay Facebook to show it (because people want their views and they want them fast) and actually lost money. What if they just focused on one thing? A business focused on referring sellers to marketplaces... a business working to sell someone else's products... they'd both be very successful at one thing instead of failing to provide on both ends