Disclaimer: All of the below is my humble opinion. Do not take it as gospel.
As with many things, the devil is in the detail.
While it is increasingly easy to make a game these days without any prior industry experience, it's the little things that seem to require industry insight.
Having worked on several indie projects (none of which have seen the light of day), I'll say that making a working game is easy. Making a polished, releasable game that is fun is a nightmarish slog of hard work.
Personal story: I once spent 10 months working on a hybrid platformer/rube-goldberg game. It was mechanically balanced, had linear difficulty progression, interesting visuals, a well written storyline that incorporated and justified game mechanics and set-pieces. But playtesting revealed that it was not fun at all, I could not pinpoint where it was failing in that regard, and I ended up shelving it.
Designing a game that manages have both widespread appeal, and a unique selling point, involves more knowing what has failed than what could succeed.
Furthermore, knowing how to market your game and get enough exposure such that your game is profitable is more about experience than anything else.
That being said, getting into the industry is nigh on impossible, especially if you're not in a game developer hub city. Here in Brisbane, Australia for instance, most would-be developers have no choice but to go indie, because there just are no job vacancies in-industry.
If you check out sites such as GameDev.net or Tsumea.com, you'll see very few job openings that don't requisite years of experience and/or published titles.
