You can't really compare the current Dreamcast scene with the late 90s Amiga scene, the world was a very different place then. There were no forums, no Kickstarter, no Facebook, and no affordable media duplication methods. It's pretty easy for a Dreamcast developer to let a small but willing audience know about their game. It wasn't really possible back then. If you look in later issues of Amiga Format there are indi developers advertising games, but a couple of low-circulation magazines wasn't enough to generate decent sales.
Indi games for the Amiga now are possible, like anything people just need to work out the economics. I imagine there are at least a couple of hundred active Amiga gamers willing to pay £20-30 for a decent new game, you just need to find a developer that is willing to make a game for that kind of money (circa 5 grand.)