I'm gonna go ahead and say that PC gaming is only declining because of the expensive technology involved and the lack of code optimization.
The cost of of building a computer to run the latest games is insane. Looking at over $1200. And for some of the parts, it's not a one time cost. You have to upgrade if you want to keep in the loop. And with newer technology coming out YEARLY now, game developers feel the need to write their game with those parts in mind, forcing people to upgrade. Parts I'm mentioning are the CPU, and video card, with RAM dependant on the type of CPU.
Meanwhile, specific game consoles are cheaper and they don't need upgrading. This is due to the fact that the game developers optimize their games to the console and squeeze the fullest potential from the system. Meanwhile, PC developers just code the game and submit their rough draft as final, not giving a shit about their audience. If it means having to upgrade, they could care less.
(and people wonder why other people pirate.)
How ya doing, buddy?