Yeah, the OP is right. I just don't get why there are so many posts and so much discussion on openings on an opening message board. Sure beats me.

People spend too much time studying openings. I am no exception. This forum shows this clearly with loads of groups on all different types of openings, one on general chess, and one on endgames. 

The endgame is obviously neglected by lots of players with explanations like "I don't get endgames". Basically this is nonsense. People who think this should study their own games: a lot are decided in the endgame, and good knowledge and skills can make a half point or even a whole point difference here.    

And then there's the middle game. 

Take tactics to start with. Most chess games are decided by tactics. It is not too difficult to get better at tactics by putting some serious work into this. You might be able to finish off your opponent when you're better, and you might avoid losing by a blunder / tactical oversight. A related topic is calculating variations. 
I am now putting a lot of work into trying to improve my tactics because I know it's a weakness of me and it costs me points.

Being or becoming good at strategy (postional play) is obviously essential as well. 

I'd say the two essential differences between a GM and an amateur are (a) GMs are better at calculating variations; (b) GMs are better at the endgame.   

It's hard work to become better at this lot though, and if you read lots of books the results (the gain) may not be obvious. You may feel you've spend a real lot of time, gained nothing and made no progress. The reason people focus on openings is the quick gain - you can throw your opening novely straight at your opponent if you're so lucky they allow it. But it's hard work and difficult to become a better player rather than one who knows lots of opening tricks.