Batting average is not the end-all stat. A few points over 600 plate appearances is as little as a fluke single a month instead of a ground out.
Walks are valuable, not just offensively but because they impose a hitter's will on a pitcher. Williams was perhaps the greatest hitter of all time in part because he refused to expand the strike zone. That was one of his hitting philosophies: make the pitcher give you a pitch to hit. And you cannot just walk a Williams or a Bonds every time up because the continual on base presence will end up worse in the end for the opposing team. Bill James ran a test comparing what would happen to an average team with a Babe Ruth who was walked every time versus a team with Ruth where he hit his career norm. The always walked Ruth team did better.
The discussion over dropping a player in this era or that one like he'd beamed down on the transporter is silly. Unless a player was raised in the era you cannot fairly gauge how he would have done because you are creating an anachronism. Think of it this way: if I beamed down to colonial New York I could hang out a sign and instantly become the most knowledgeable medical practitioner of the age, even though all I have is a decently educated layman's knowledge of first aid and medicine. I know CPR, the Heimlich, germ theory, and a bunch more techniques and facts that were unknown at the time but are basic first aid standards today. It would be an anachronism, same as parachuting Mike Trout into a deadball era game.
Pitching speed is an interesting issue that I feel has been misinterpreted in some posts here. If the average guys today are faster than before, in the low 90s and a flamethrower is around 98-101, what makes the average guy so much faster than the old timers? It isn't that the upper end of speed has expanded. What fascinates me is not that the average pitcher today is faster but that the outlier, the fastest, is still around 100-105 MPH. That has remained consistent for as long as we have been able to measure accurately (e.g., Ryan and Feller, #1 and #2 for a single pitch). What that tells me is that there is a mechanical limit to pitching speed regardless of technical perfection. I am guessing that Johnson and Grove at their best approached that limit and would still be elite power pitchers if they were raised and trained today, because they were the outliers of their era. My speculation also is that the average guy today may throw faster than the average 100 years ago because of better technique and training. But technique and training benefits the elite guys too. Here are two images of Clayton Kershaw from May:
When I got the cards I was struck not by how consistent his motion is, but how textbook it is for modern mechanical teachings for pitchers: balance, leg drive, no inverted W arm, etc. That is not unusual today. Pitchers today have been carefully trained to have very sound mechanics. It was unusual even 50 years ago to see a wide variance in motions because oddball pitchers who were effective were not trained otherwise. Marichal's leg kick, Spahn's windmill, Tiant's no-look, Gibson's fall off the mound, all would not have survived training. Might have made them better or perhaps not, even though it does make the average guy better to have a more consistent and efficient technique. So the lower end of the spectrum rises (average speed) but the elite flame throwers still hit around 100-105 because the amount of force an arm can generate is limited by basic structural factors: how much load can the bone take, how much leverage can be generated by the motion, etc.