Probably the internets fault.
Before the internet really became big, you would just go into a store and see a box art and buy a game. Go home and find out if it is fun or not. Heck, you hardly even knew a game was coming out until it was out.

Come internet and you know years in advance and all you have to look forward to is trailer and pics for months/years until the game releases. People spend longer waiting for a game than playing it, thus they want pretty pictures and cool vids to show people of what they are going to be playing for a few weeks when it comes out. Then on to next hyping of cool looking game.

I don't think it's that badly as people make it out to be, but I think graphics are a game's first impression. A game with bad/dated graphics can turn off some people from the get-go. It's not always the case, of course. If the visual of a game look dated but there is a good uniqueness or corkyness to it, it can be overlooked.

Great graphics doesn't mean you get an instant pass, just look at Ryse for the X1 and Killzone for the PS4, fantastic looking games that were panned for their gameplay/story/shallowness, etc. The Order for PS4 is another great example, fantastic graphics and art design bugged down by monotonous gameplay and an unsatisfying story.

We really should not judge a book by its cover but it's often hard not to. Great games come from a mixture of great graphics, solid gameplay and well-paced story telling, extremes are often bad. Ultimately, i agree that gameplay should be more important or there should be more focus on perfecting the gameplay than graphics and I say that as a staunch Sony fanboy but Nintendo "limiting" (IMO, can't stress that enough) their franchises to fairly weak consoles just frustrates me, personally. At the end of the day though, I'm not interested in their console or software offerings so they can do whatever they think is best.

Since jaggies started to damage people's eyes.