Actually, today's pitchers are bigger an stronger than they've ever been.
But, in order to succeed, they have to employ maximum effort on just about every pitch. Because the hitters are also bigger and stronger than they've ever been.
Moreover, it requires more pitchers to complete an average inning. About 15-16 is the optimum nowadays.
Pitch counts are way up from the twenties, the fifties, even the seventies. That's because batters take more pitches now, waiting for a pitch they can drive. This has proven to be a productive offensive strategy -- it results in more power, more runs.
As a result, walks and strikeouts have multiplied -- and those 5-and-6 pitch ABs are replacing the 1-and-2 pitch ABs that were common earlier in the game's history -- when there was an onus against striking out.
Go to Baseball Reference and check the hitting and pitching league leaders for walks and strikeouts between today and, say, 1952. You'll be stunned.
We've only got pitch counts for the last 30-or-so years, but it's believed that sixty years ago, it took an average of 80-90 pitches to work a complete game. Today, the average would top 150.
Also, pitchers are generally less effective the more times through a line up. The more times a hitter gets a look at release point and timing of the delivery the better it is for the hitter. Eventually we might see someone finally try some sort of rotation where a pitcher only pitches once or twice to every batter. It will probably take a bad rebuilding team with maybe one or two guys that pitch crazy innings like knuckleball guys to take up the slack in blow outs.
Freegards
They might be bigger and stronger, but they pitch fewer inning, half of them never have to hit (soon all), and they’re good at fewer pitches. The expectations for pitchers are diminishing.