Even if Valve holds a significant market share of the PC Gaming market, this is a harsh conclusion. There are other significantly more expensive and restrictive options, such as the Windows Store for Windows, or the Play Store for Android, or the App Store for iOS and MacOS. PC has much free-er and more accessible options for indie developers, like itch.io. It's probably the least monopolistic gaming market out there. The struggle of course is advertising and reach, not sure who the gate keepers for that were with TTD, maybe magazines?