I've spoken to this before, but since it's a passing parade and the line has moved along, I thought I'd mention it again.
Much of what I have learned in my life has gone from the broad and general to the specific. You establish a beginner's base and then add to that.
You don't build a pyramid with the point down.
If you want to learn to swim, starting in shallow water where you can touch the bottom if you lose your stroke is maybe safer than doing it in deep water where you cannot.
Once you learn the basic stroke, you can swim in any depth. And then you can add other strokes, increase your distance, become more adept. If you want to win an Olympic event as a swimmer, you have to master one or more strokes, become efficient, develop specific strengths, and train out the wazoo to get to world-class status. The level of competition is going to be a lot higher than it is down at the open swim for seniors Wednesday at the local pool.
I'm guessing most of you are still with me.
General is good, and sometimes enough to do what you need to do. And that's where you start. If you can throw a fist-sized rock, you can probably throw a baseball. (If you want to throw it in the major leagues, you need more depth. Michael Jordan, arguably one of the greatest basketball players ever, was fit, trained, and beyond expert in his sport, but when he went to play minor league baseball, it didn't translate. Probably he was in better shape than most of the players around him generally, but his depth in baseball was lacking. He might have learned, but he was way behind the curve, and chances are he wouldn't have ever caught up with guys who had been specializing in the sport all their lives.)
Training in two-move chess problems seriously for fifty hours will put a so-so player on a par with grandmasters–for two-move chess problems. You won't have his total game, but in a heads-up in that particular arena, you can hold your own.
It depends on what you want or need to do.
Sometimes wide and shallow is the ticket. Jack of all trades, master of none.
Sometimes, deep and narrow beats wide and shallow all to hell and gone.
The trick is to know which one best serves you in a given situation.