Because it only runs on Microsoft's platforms. The whole point of it is to keep developers on MS platforms. It is anti-competitive. On the other hand, open-source libraries flourish even without competition.
No, they're badly losing to Sony in that area in the latest generation of consoles. I'm more worried about games (and, more importantly, other graphical applications) on Windows using DirectX.
Because it only runs on Microsoft's platforms. The whole point of it is to keep developers on MS platforms. It is anti-competitive. On the other hand, open-source libraries flourish even without competition.
No because Metal isn't a threat to competition. If Apple were cornering the market with Metal, yes, I'd be against it too. If Apple cornered any market, I'd be very scared (imagining Macs being restricted to the App Store), but that's not going to happen either with Mac or iOS since they cater only to the high end and operate high-margin. Microsoft's the one to worry about because they go for market share at all costs.