Gaming on the PC is not dead, even though some have been claiming the end is near for at least ten years now. But, gaming on the PC has changed quite a bit in the last decade. If you look at the gaming environment on the PC a decade ago, a bit longer even, in the late 90s with the launch of the first GeForce... gaming on the PC was a much larger affair - big budget games that took a big budget PC to play. Developers expected PC gamers to be on the bleeding edge, and for the most part they were. Sure, some developers tried to market to the low-end niche. But the general sense seemed to be, if you were gaming on the PC you had a beast of a rig for it, and all the big budget developers tailored their games with that in mind.
Now things have really changed. There a lot more PCs out there, but the high-end gaming enthusiast is a very small portion of computer users. So developers, with a few exceptions, tend to target those low to mid range systems out there, since that's where the market is... it's no longer reasonable for developers to expect a gamer to have a state of the art system. As a good example to this, I can't help but mention the elephant in the room when it comes to PC gaming: World of Warcraft. Easily one of the most popular PC games in the world. While WoW obviously requires more hardware than your average Facebook game, it's really not by much. They've made sure to design the game so it will run on a very low end machine, like the kind you can pick up at Walmart for under $500. Now, a game like WoW does have advanced shader features and DX11 stuff that can be toggled on for those with higher end systems, but none of it is required. Sure, the higher end machines make it look better and run faster, but it's a huge shift from the late 90s where developers just expected gamers to have high end machines to play their games at all.
Now, before someone points out that my example, WoW, is already several years old, I would point that Blizzard just released an expansion at the end of 2010, and if they wanted they could have totally reworked the game engine for high end systems (while that would be an expensive endeavour, if anyone could afford to it's Blizzard). They did not though, because Blizzard knows that having more systems able to run the game increases the potential market.
That's not to say games for high end systems don't exist on the PC anymore, since they obviously do, but they seem to be the exception instead of the norm these days. And a lot of those high end games are cross-platform, so they only require high end systems because they're competing with the current generation of consoles (which, I admit, isn't hard given this generation of consoles seems to have outlived all previous generations). I guess my long-winded point here is that the landscape of the PC gaming world has changed. High end systems are no longer the default assumption like they were a decade ago. I think overall this is good for gamers, since instead of being an expensive niche hobby, PC gaming is within the reach of anyone who can own a very modest PC.