I know that when my life is out of order in all sorts of ways, I'll start obsessing about keeping my place clean. Because it's something I can control. I can actually be quite a bastard when this happens. The same things draw people to eating disorders or fancy cars or any number of other things.
So, if you are a photographer, you cannot necessarily control inspiration or weather or your subjects or anything else. You can't even buy these things. All of the courses in the world aren't going to show you how to think like you are supposed to. The greatest models in the world still look bad if you don't get them from the right angle.
So, photographers obsess over sharpness instead, because they can control that. They can analyze and understand the sharpness of an image and quantify it. And you can agree on things.
Now, after a while you do realize that some shots are going to really look better when they are sharp and printed huge, which really does require good hardware as well as a talented photographer behind the camera. I've taken plenty of shots where it's technically very sharp and high resolution, but simply lacks any sense of emotional intensity.
This isn't just a harmless pursuit, mind you. If you get a beginner all turned around and obsessed with taking the most sharp pictures possible, they won't learn about composition or rapport with subjects or timing or lighting. A photographer who's shots aren't quite sharp enough can eventually upgrade to sharper gear, but a photographer who sucks will continue to suck regardless of their gear or sharpness.
I should also note there are always major exceptions to any pat argument.
You should realize that certain styles of photography and viewing settings REQUIRE a sharp set of equipment. If you want to make beautiful landscapes like Arizona Highways, you really need a 4x5.
On the other hand, artistic use of blur, like pinholes and zone plates and Holgas, can be very beautiful.
Either way, have confidence that the folks who yammer on about how your camera doesn't matter are just as dumb as the people who shoot mostly test charts. Except that most of the folks who yammer on about either side of the argument are trying to get you to link to their blogs so as to get hits for various nefarious schemes.
Including this site, of course. :)