I watched a very successful HS coach who lived and died with the hit the "First Fastball Strike" philosophy.
It worked for most HS hitters since most couldn't consistently hit a good fastball - much less a mediocre to average breaking ball. This was true of his team and it had 10 kids play DI baseball, won a state championship and finished in the top 30 in several national polls.
The problem was when he had players that had been taught to hit correctly and could hit breaking balls with two strikes and take the outside pitch the other way. He turned a couple of kids I knew very well that did a nice job of being selective line drive hitters into ground ball machines afraid to take pitches out of fear of being taken out of the lineup. A fastball "Strike 1" was cause for a huffing, puffing stomp around the coaches box at 3rd base. God forbid there were runners.
So like anything else - need to be able to assess your players and the pitching they are facing and get a balanced philosophy. Also it doesn't hurt to have some flexibility and not be dogmatic across the board with any particular approach in this regard.